SMTP Status Codes What the message may mean
\n101 – Cannot open
\nconnection
\n(also called SMTP Error 1.0.1)
\nSMTP Error 101 : Typically your SMTP server or email
\nprogram is unable to even start an SMTP session. Typical
\nreplies will be “SMTP Error 101, Error opening connection”
\nor “SMTP Error 101, cannot open SMTP stream”.
\nAll SMTP Error 101 errors usually point to a configuration
\nproblem, such as an incorrectly spelt SMTP server, or an
\nIP address that does not exist, or an SMTP port that does
\nnot exist or which the recipient will not accept SMTP
\nconnections on, or some other process is already using the
\ndefault SMTP port, port 25.<\/p>\n
211 – System Status
\nmessage or System
\nHelp Reply
\n(also called SMTP Error 2.1.1)
\nSMTP Error 211 : SMTP status 211 prefaces a message
\nabout the Mail Server status or a System Help reply to the
\nuser requesting help information. You might for example
\nissue a command to the mail server to display a list of
\ncommands you can use and the server replies with an
\nSMTP Reply 211 followed by the list you requested.
\n214 – Help Reply message (also called SMTP Error 2.1.4)
\nSMTP Error 214 : SMTP status 214 is usually in reply to
\nthe “HELP” command. It displays information about the
\nserver, usually a URL to the FAQ page of the SMTP
\nsoftware running on the server. As a result this “error” is
\nnormally called a reply, as in SMTP Reply 214.<\/p>\n
220 – <Server Name> service is running (also called SMTP Error 2.2.0)
\nSMTP Status 220 : This is normally the first message you
\nwill get back from the server. It means the mail service is
\nrunning (ie. your mail server is running). It will normally
\ncontain a welcome message and\/or the title of the SMTP
\nsoftware and, sometimes, the version number of the mail
\nserver software. SMTP Reply 220 is effectively a “Hi
\nThere, I have just this second finished starting up – I
\nam ready to go and at your command” informational
\nmessage.<\/p>\n
221 – The domain service is closing the transmission channel (also called SMTP Error 2.2.1)
\nSMTP Error 221 : The server is ending the mail session –
\nit is closing the conversation with the ISP as it has no more
\nmail to send in this sending session.
\nSMTP Status 221 is often misconstrued as an error
\ncondition, when it is in fact nothing of the sort. The mail
\nserver is simply telling you that it has processed everything
\nit was given in this particular session, and it is now going
\nback into waiting mode.
\nBecause SMTP status 221 is often misinterpreted, with
\nsome mail servers the Network Administrators have
\nchanged the default text of SMTP Reply 221 to something
\nmore meaningful and less alarming. For example, a typical
\nSMTP reply 221 might say “221 Goodbye” or
\n“221 Closing connection”, or the most irritating one we’ve
\nseen “221 Bye”, Arrrgghh – can you blame anyone for
\nthinking there might be a problem ? Of course not ! So
\nsome Network Administrators are these days being quite
\nimaginative by changing the default text of SMTP reply 221
\nto more user friendly messages like : “221 Thank you for
\nyour business” (I love that one!), or “221 All messages
\nprocessed successfully in this session, SMTP connection
\nis closing”.<\/p>\n
250 – Requested mail
\naction OK completed
\n(also called SMTP Error 2.5.0)
\nSMTP Status 250 : The mail server has successfully
\ndelivered the message! This is the best SMTP reply (250)
\nto receive – your message has been accepted and
\ntransmitted OK ! J Yippee.
\n250 is effectively a status code rather than an error code –
\nthere is no such thing as an SMTP error 250.
\n251 – User not local will
\nforward
\n(also called SMTP Error 2.5.1)
\nSMTP Status 251 : The email account is not local to the
\nISP server but the ISP server will accept the email and will
\nforward it (the server will RELAY your message, this is the
\nmost common action for ISP Mail servers – the recipient
\nwill see your ISP in the mail header as one of the first hops
\non the way to the recipient’s email system).
\nSMTP Error 251 is therefore more of an informational
\nmessage for technicians tracking how a message reached
\nits destination.<\/p>\n
252 – Cannot VRFY (verify)
\nthe user – the server
\nwill accept the
\nmessage and attempt
\nto deliver it
\n(also called SMTP Error 2.5.2)
\nSMTP Status 252 : The user account appears to be valid
\nbut could not be verified, however the server will try do
\ndeliver the message.
\nThere are sometimes circumstances where an email
\naddress appears to be valid but cannot be verified as
\ndefinitely valid during the SMTP session between the
\nsending server (your server) and the next server to accept
\nyour message. This can happen for example in very large
\ncorporation where the first email receiving server might
\nonly be an email exchanger server, a gateway server to
\nthe eventual server which holds the user mailboxes and
\nwhich can verify if the intended recipient exists in that
\norganization. When this happens the gateway server will
\nreply with an SMTP Error 252 telling your sending server
\nthat it cannot verify the user part of the email address, that
\nthe domain part is OK, and that it will forward your email to
\na server which can do the checking and eventually deliver
\nto the user mailbox if it exists.<\/p>\n
354 – Start mail input end
\nwith <CRLF>.<CRLF>,
\nor, as a less cryptic
\ndescription – “FROM
\nand TO information
\nreceived, now please
\nprovide message
\nbody and mark its
\nend with
\n<CRLF>.<CRLF>”
\n(also called SMTP Error 3.5.4)
\nSMTP Error 354 : This is normally in response to the
\nDATA command. The server has received the From and
\nTo information and is now asking for the “Message
\nBody”, the main part of the message which should be
\nended by two blank lines separated by a dot (period).
\nTherefore, on receiving an SMTP Reply 354 the sending
\nserver should send the body of the message to the
\nreceiving server and indicate the end of the message body
\nwith <CRLF>.<CRLF> (note the full stop between the two
\nCarriage_Return-Line_Feed’s).<\/p>\n
421 – <Server name>
\nService not available
\n– the sending email
\nprogram should try
\nagain later
\n(also called SMTP Error 4.2.1)
\nSMTP Error 421 : The Mail transfer service is unavailable
\nbecause of a transient event. SMTP reply 451 can be
\ncaused by many things but generally indicates that the mail
\nserver which returns this status code is currently
\nunavailable but may be available later.
\nFor example, the server administrator may have stopped
\nthe mail service to troubleshoot a problem, or the mail
\nserver is right in the middle of rebooting, or the mail server
\nis currently processing too many incoming messages or
\nincoming requests, etc…. Note : “Mail Server” in this
\ncase can be any of the mail servers on the message’s
\nroute – the sending server (your server), the ISP SMTP
\nserver, or the recipient’s mail server.
\nClearly, if you repeatedly receive an SMTP status 421 then
\nthe problem is no longer of a transient nature and you
\nneed to investigate or inform the relevant network
\nadministrator, ISP tech support, or the recipient.<\/p>\n
422 – The recipient’s
\nmailbox is over its
\nstorage limit
\n(also called SMTP Error 4.2.2)
\nSMTP Error 422 : Either the recipient’s mailbox is over its
\nstorage limit or the message delivery directory (folder) on
\nthe recipient’s mail server is currently over a size limit
\nimposed by the Network Administrator (e.g. possibly as a
\nresult of the mail server having been down for some time,
\nhaving been repaired, and currently in the process of
\ncollecting thousands of queued up messages).<\/p>\n
431 – The recipient’s mail
\nserver is experiencing
\na Disk Full condition
\n(also called SMTP Error 4.3.1)
\nSMTP Error 431 : The recipient’s mail server is
\nexperiencing a Disk Full error condition, or an Out of
\nMemory (too many file handles) error condition (Microsoft
\nExchange).<\/p>\n
432 – The recipient’s
\nExchange Server
\nincoming mail queue
\nhas been stopped
\n(also called SMTP Error 4.3.2)
\nSMTP Error 432 : This is an SMTP status response
\nspecific to Microsoft Exchange Server. It indicates that the
\nrecipient’s mail queue on their Exchange Server has been
\nstopped (frozen), probably while the Network Administrator
\ntroubleshoots some problem.<\/p>\n
441 – The recipient’s server
\nis not responding
\n(also called SMTP Error 4.4.1)
\nSMTP Error 441 : This is an error emanating from your
\nserver indicating that the recipient’s server is not
\nresponding. Your server will automatically try again a
\nnumber of times – how many depends on how your server
\nhas been configured.<\/p>\n
442 – The connection was
\ndropped during
\ntransmission.
\n(also called SMTP Error 4.4.2)
\nSMTP Error 442 : Your server started delivering the
\nmessage but the connection was broken during
\ntransmission. This may be an unusual transient error –
\nhowever, if it keeps happening you should investigate
\npossible problems with your server’s network card, your
\nInternet routers, processes hogging the resources of your
\nserver, and anything else which could result in a network
\nconnection being broken.<\/p>\n
446 – The maximum hop
\ncount was exceeded
\nfor the message
\n(also called SMTP Error 4.4.6)
\nSMTP Error 446 : The maximum hop count was
\nexceeded for your message. The most likely cause of this
\nerror status code is that your message is looping internally
\non your server, internally between two of your
\norganisation’s servers, or, sometimes, looping between
\nyour server and the recipient’s server.<\/p>\n
447 – Your outgoing
\nmessage timed out.
\n(also called SMTP Error 4.4.7)
\nSMTP Error 447 : Your outgoing message timed out
\nbecause of problems with the receiving server who
\nobjected to your message. Typically there is a problem
\nwith the message header (such as too many recipients, in
\nmost cases, or a protocol timeout between the two
\nservers).<\/p>\n
449 – Routing error
\n(also called SMTP Error 4.4.9)
\nSMTP Error 449 : This is a Microsoft Exchange Server
\nspecific error code. As per Microsoft’s documentation this
\nerror code is returned when either of the following
\nconditions occurs : an SMTP connector is configured to
\nuse DNS without a smart host and also uses a non-SMTP
\naddress space (e.g. X.400), or A message was sent to a
\nrecipient who was identified as a member of a routing
\ngroup that was deleted.
\nMicrosoft recommends using the WinRoute tool to
\ntroubleshoot this error (Microsoft Knowledgebase article
\n281382)<\/p>\n
450 – Requested action not
\ntaken – The mailbox
\nwas unavailable at the
\nremote end. A
\nsecondary SMTP
\nerror code may follow
\n“450” to refine the
\nreason for the failure
\nto transmit the
\nmessage, e.g.
\n“SMTP Error 450
\n(also called SMTP Error 4.5.0)
\nSMTP Error 450 : The server could not access the
\nmailbox to deliver the message. This could be caused by
\na process on the remote server tidying up the mailbox, or
\nthe remote mailbox could be corrupt, or the remote mailbox
\nmay be stored on another server which is currently offline,
\nor the network connection went down while sending, or the
\nremote mail server does not want to accept mail from your
\nserver for some reason (IP address, blacklisting, etc..).
\nIn general SMTP Error 450 is a transient error at the
\nremote end (the destination), or at one of the servers
\nen route to the remote end, and should induce your
\nmail server to retry after it’s preset retry interval.
\nExample of an SMTP Error 450 reply message : “450
\nPlease try again later”.
\nSMTP Error 450 is often followed by a second SMTP error
\ncode to refine the reason for the email not reaching its
\ndestination. For example : “SMTP Error 450 5.2.3 Msg
\nSize greater than allowed by Remote Host”. When that is
\nthe case and If the error message is not as clearly worded
\nas in this example, then simply search this document for
\nthe secondary error code. In this case searching this
\ndocument for SMTP Error 523 or SMTP Error 5.2.3 would
\nyield an explanation identical to the wording above.
\n451 – Requested action
\naborted – Local error
\nin processing.
\n(also called SMTP Error 4.5.1)
\nSMTP Error 451 : The action has been aborted by the
\nISP’s server. “Local” refers to the ISP’s server. This
\nerror is usually due to overloading at the ISP from too
\nmany messages or transient failures. Typically some
\n[hopefully] temporary event prevents the successful
\nsending of the message. The next attempt to send by your
\nserver may prove successful.
\nIf this error keeps occurring to the point that it has
\neffectively lost its transient nature and has become
\n….. frequent (!!), then the problem is at your end and
\nyou should check your own mail server (if you email out of
\na corporate network), communications on your side (router,
\nserver network card), or inform your ISP if your mail server
\nrelays through your ISP or if you are a home user emailing
\nout through Outlook, Outlook Express, Windows Mail, or
\nsimilar email program.
\nExample of typical SMTP Error 451 return messages :
\n“SMTP error 451 Unable to complete command, DNS not
\navailable or timed out” or “451 Domain of sender address
\ndoes not resolve” or “451 Error getting LDAP results in
\nmap”.<\/p>\n
452 – Requested action not
\ntaken – Insufficient
\nstorage.
\n(also called SMTP Error 4.5.2)
\nSMTP Error 452 : The ISP server’s disk system has run
\nout of storage space, so the action had to be cancelled.
\nUnless you are with an ISP which is so slack that they
\nhave not implemented Disk Full Alerts, this error usually
\nindicates that your ISP’s mail server is overloaded from too
\nmany messages. This can happen even to the best ISPs
\nwhen, for example, there have been problems and none of
\nthe ISP’s customers could send mail; as soon as the
\nproblems are fixed there is almost always a situation where
\nthousands of users and organizations are trying to send
\nmail all at the same time, and those numbers can
\noccasionally result in the ISP’s mail servers’ hard disks
\ntemporarily filling up, with SMTP Error 452 being the result.
\nThe next attempt to send by your server may prove
\nsuccessful.
\nSMTP Error 452 : Most ISPs mail servers impose a
\nmaximum number of concurrent connections that client’s
\nmail servers can attempt to make, and they usually also
\nhave a limit on the number of messages that are sent per
\nconnection. With business customers these maximums
\nare rarely reached, if ever. Nevertheless, If you have a lot
\nof messages queued up, for example as a result of the
\nconnection to your ISP going down for a significant amount
\nof time (and you have hundreds of users in your
\norganization, or it happened just as you were about to
\nsend that large mailshot!), there could be a situation where
\nthe output of messages from your server goes over the
\nmaximum number of messages per connection allowed by
\nyour ISP. This is another case where the ISP’s server may
\nissue a 452 SMTP error. As above, the next attempt to
\nsend by your server may prove successful.
\nSMTP Error 452 : This error can also be indicative of a
\nproblem on your own mail server. Here is an example of
\nan SMTP 452 error : “”452 Out of memory”<\/p>\n
465 – Code Page
\nunavailable on the
\nrecipient server
\n(also called SMTP Error 4.6.5)
\nSMTP Error 465 : This is an Exchange Server-specific
\nerror code. This error is returned by the recipient’s server
\nif the incoming email specifies a Code Page that is not
\ninstalled on the recipient’s server, normally because not all
\nlanguage files were installed on the server during either the
\ninstallation of Windows or of Exchange Server.<\/p>\n
471 – This is a local error
\nwith the sending
\nserver and is often
\nfollowed with “Please
\ntry again later”
\n(also called SMTP Error 4.7.1)
\nSMTP Error 471 : This is always a local error with your
\nown mail server. SMTP Error 471 (or 4.7.1) is usually
\ntagged onto a primary SMTP error code, for example
\n“SMTP Error 450 4.7.1”, or “SMTP Error 451 4.7.1”, or
\n“SMTP Error 550 4.7.1”. In all the cases that we have
\nseen SMTP Error 471 is usually caused by anti-spam or
\nvirus scanning software on your server (the sending
\nserver) getting into problems through a bug in the software,
\nor because of a bad automatic update from the
\nantivirus\/anti-spam manufacturer, because of lack of
\nmemory on your server, or because of hard disk problems.<\/p>\n
500 – Syntax error
\ncommand not
\nrecognized.
\n(also called SMTP Error 5.0.0)
\nSMTP Error 500 : The last command sent by your server
\nwas not recognized as a valid SMTP or ESMTP command,
\nor is not formatted in the way the server expected. This
\nincludes situations where the command is too long.
\nNote that commands that are recognized, but not
\nimplemented, are handled by different status messages
\n(see 502 and 504).<\/p>\n
501 – Syntax error in
\nparameters or
\narguments (e.g.
\ninvalid email address)
\nCan sometimes also
\nbe indicative of
\ncommunication
\nproblems
\n(also called SMTP Error 5.0.1)
\nSMTP Error 501 : The command was correct and
\nrecognised, but the parameters (the arguments, e.g. email
\naddress) were not valid.
\nFor example, the following email address will definitely give
\nan SMTP Error 501 with most mail servers,
\nhappy\\_larry@hotmail.com, as “\\” is not allowed in email
\naddresses, which makes this email address invalid.
\nIn the vast majority of cases SMTP Error 501 is caused
\nby invalid email addresses. For example, a typical return
\nerror message might be : “<remote-server-ip-address>
\ndoes not like recipient. Remote host said: 501 Invalid
\nAddress”.
\nIn cases where the error is not caused by an invalid email
\naddress, an SMTP Error 501, particularly if repeated, can
\nbe indicative of communications problems, such as a noisy
\nline, intermittent drops in network connections, etc…<\/p>\n
502 – Command not
\nimplemented.
\n(also called SMTP Error 5.0.2)
\nSMTP Error 502 : The command or function issued by
\nyour mail server is valid but has not been activated
\n(typically, it is not supported on this particular server).<\/p>\n
503 – Bad sequence of
\ncommands.
\nor
\nThis mail server
\nrequires
\nauthentication
\n(also called SMTP Error 5.0.3)
\nSMTP Error 503 : In the original standards SMTP Status
\n503 indicates that the commands have been sent in the
\nwrong order, for example your mail server has sent the
\n“Hello” command before sending the “Mail” command.
\nThis can often be caused by a drop in network connection
\njust as your server was sending a command, resulting in
\nthe ISP’s server not receiving it and consequently not
\nunderstanding the command that followed it.
\nNote : this error, particularly if repeated, can be indicative
\nof communications problems, such as a noisy line,
\nintermittent drops in network connections, etc…
\n——————————
\nSMTP Reply Code 503 is nowadays more often an
\nindicator that the SMTP server you are trying to use
\nrequires authentication and you tried to send a message
\nwithout authentication (username + password). This
\nSMTP Error 503 is permanent in that the SMTP server, will
\nnot log any errors in its log and it will not retry – you will
\nhave to resend the email using authentication. Example of
\nsuch an error : “SMTP Error (state 13): 503 This mail
\nserver requires authentication when attempting to send to
\na non-local e-mail address. Please check your mail client
\nsettings or contact your administrator to verify that the
\ndomain or address is defined for this server.”.<\/p>\n
504 – Command parameter
\nnot implemented.
\n(also called SMTP Error 5.0.4)
\nSMTP Error 504 : The command and parameter are both
\nvalid, but the parameter is not implemented on the ISP
\nserver, or an additional parameter or action is missing.
\nFor example, an often encountered SMTP Error 504 is :
\n“504 Need to authenticate first”.<\/p>\n
510 – Bad Email Address
\n(also called SMTP Error 5.1.0)
\nSMTP Error 510 : Bad email address. This status code
\nis generated by the sender’s local mail server.
\nIf the email was addressed internally, then it means that
\nthe addressee, as written in the email’s TO, CC, or BCC
\nfields, does not exist in your organization’s email system.
\nIf the email was addressed externally, then the recipient’s
\nemail address was misspelt.<\/p>\n
511 – Bad Email Address
\n(also called SMTP Error 5.1.1)
\nSMTP Error 511 : Bad email address. This error is
\nsimilar to error 510 and as with error 510, this status code
\nis generated by the sender’s local mail server.
\nIf the email was addressed internally, then it means that
\nthe addressee, as written in the email’s TO, CC, or BCC
\nfields, does not exist in your organization’s email system.
\nIf the email was addressed externally, then the recipient’s
\nemail address was misspelt.<\/p>\n
512 – The host server for
\nthe recipient’s
\ndomain name cannot
\nbe found (DNS error)
\n(also called SMTP Error 5.1.2)
\nSMTP Error 512 : This SMTP reply code is received
\nwhen one of the servers on the way to the destination is
\nunable to resolve the domain name of a recipient email
\naddress. Said differently : one of the servers on the way
\nto the destination, including your server or your ISP, has a
\nDNS problem or, possibly correctly, does not like one of
\nthe email addresses in the message’s TO, CC, and BCC
\nfields.
\nThe first check you should perform to resolve a 5.1.2 reply
\ncode is to check all the recipient email addresses for
\nincorrect domain names (misspelt domain names, or,
\nmaybe, totally non-existent domain names) – remember,
\nerror code 512 is very specifically an error with the
\ndomain name of one of the recipient email addresses.
\nYou can call the recipient(s) or use the WHOIS tool of The
\nUltimate Troubleshooter. If all the recipient email
\naddresses check out as regards the domain part of the
\nemail addresses, then one of the servers on the way to the
\nrecipient(s) has DNS problems – usually this will be one of
\nthe first 2 servers in the chain, your own mail server (or
\nyour network) or your ISP’s mail server.
\nExamples of typical SMTP error 512 messages : “5.1.2 –
\nBad destination host ‘DNS Hard Error looking up domain”,
\nor “SMTP Error 550 5.1.2 Host unknown – host cannot be
\nfound”, or how about this fantastically informative error
\nmessage “5.1.2 The message could not be delivered
\nbecause the recipient’s destination email system is
\nunknown or invalid. Please check the address and try
\nagain, or contact your system administrator to verify
\nconnectivity to the email system of the recipient.”.
\n————–
\nIn summary : most SMTP error 512 conditions are
\ncaused by misspellings of the domain name part of a
\nrecipient email address. However, with the proliferation
\nof spam, error 512 is also often encountered by automatic
\n“out-of-office” replies to junk mail because the domain
\nnames used by junk mail are often bogus domain names.
\n513 – Address type is
\nincorrect (most mail
\nservers)
\nor
\nRelaying denied or
\nAuthentication
\nrequired (a small
\npercentage of mail
\nservers)
\n(also called SMTP Error 5.1.3)
\nSMTP Error 513 : This status code (from the sender’s
\nmail server) is usually symptomatic, in an Exchange +
\nOutlook environment, of the user’s Outlook Contacts
\nhaving been imported from another system or PST and
\nwhere some of the addresses are not defined correctly.
\nOr, in any environment it is simply that the end-user simply
\ndid enter the email address completely wrongly, such as
\ncopying it from a website and not replacing “at” with “@”,
\ne.g. : John.DoeatUCLA.edu (which should have been
\nJohn.Doe@UCLA.edu), or John.Doe@UCLA.edu” (“,
\nquotes, is not allowed in email addresses and is often
\nincluded in error as a result of copying and pasting an
\nemail from somewhere).
\nThe user should check all the recipient addresses in the
\nemail, including those that were inserted from Contacts.
\nNote : the SMTP reply code 5.1.3 is often a secondary
\nreply code. Some mail servers, for example, might reply
\n“SMTP error 501 5.1.3 Invalid address”, or “SMTP error
\n553 5.1.3 User address required !”, or “SMTP error 501
\n5.1.3 Bad recipient address syntax”, or “SMTP error 513
\nRelaying Denied – Can not send e-mails to some
\naddresses”, or this excellently informational Exchange
\nServer 2007 error (the whole error message is in green
\nbelow) :
\n“SMTP error 550 5.1.3 STOREDRV.Submit; invalid
\nrecipient address.
\nDelivery has failed to these recipients or distribution lists:
\nThe format of the recipient’s e-mail address isn’t valid. A
\nvalid address looks like this: username@microsoft.com.
\nMicrosoft Exchange will not try to redeliver this message
\nfor you. Please check the e-mail address and try sending
\nthe message again, or provide the following diagnostic text
\nto your system administrator.
\n5.1.3: The format of the recipient e-mail address is not
\nvalid. Valid SMTP e-mail addresses can contain only
\nletters, numbers, hyphens, periods, and only one @
\nsymbol. Troubleshooting: Verify that the SMTP address of
\nthe recipient is formatted correctly and resend the
\nmessage.”
\n————–
\nSMTP Error 513 is also used by a small percentage of
\nmail servers to indicate a completely different error, namely
\nthat you need to authenticate to the mail server before
\nbeing able to send your message (SMTP authentication).
\nA typical error message might be : “SMTP error 553
\nAuthentication is required to send mail as
\nusername@ispdomainname.com”.
\nIn such cases you simply need to configure your mail
\nserver, or your email program to send emails with SMTP
\nauthentication.<\/p>\n
523 – The Recipient’s
\nmailbox cannot
\nreceive messages
\nthis big
\n(also called SMTP Error 5.2.3)
\nSMTP Status 523 : This error will be received when the
\ntotal size of the message you have sent (ie: message + all
\nof its attachments) exceeds the size limits on the
\nRecipient’s server. Many companies implement the good
\npractice of configuring their servers with limits on the size
\nof emails they can receive to prevent their systems running
\nout of space as a result of a spam attack where the spam
\nemails contain large attachments, or as a result of valid but
\nnot very technically savvy senders sending enormous
\nscans (through not knowing that scanning at 1200dpi
\nrather than the usually perfectly usable and acceptable
\n300dpi, will create humongous attachments).
\nCheck the size of the email you sent, and, specifically, the
\nsize of the attachments you included, and consider splitting
\nyour email into smaller emails. If that does not work, check
\nwith the Recipient the maximum size of email they can
\nreceive, and if that is still prohibitive then consider FTP
\narrangements between you and the recipient.
\nSMTP Error 523 is often a secondary SMTP error code
\nrather than a primary error code, as in the following
\nexamples : “SMTP Error 450 5.2.3 Message Size greater
\nthan allowed by Remote Host” or “SMTP Error 552 5.2.3
\nData size exceeds maximum permitted” or “SMTP Error
\n552 5.2.3 Message exceeds maximum fixed size”, and so
\non ….<\/p>\n
550 – Requested actions
\nnot taken as the
\nmailbox is
\nunavailable.
\n(also called SMTP Error 5.5.0)
\nSMTP Error 550 : This response can be caused by quite
\na few situations.
\n————–
\nSMTP Error 550 will be returned by many servers If the
\nrecipient email address simply does not exist on the
\nremote side (you will often get “550 Invalid recipient” or
\n“550 User account is unavailable” or “<ip-address-ofremote-
\nserver> does not like recipient – 550 Address
\nrejected” or “550 No such user here” or “550 Not our
\nCustomer” or “550 Account not available” or “Remote
\nhost said : 550 – Barack.Obama@ThisCompany.com, this
\nTHISCOMPANY.COM Mailbox Does Not Exist – Giving
\nup”). In this case the sender of the email needs to contact
\nthe recipient verbally to get the correct email address.
\n————–
\nSMTP Error 550 will sometimes also be returned by the
\nrecipient’s anti-spam firewall if, for example, the
\nanti-spam firewall does not like the sender (typically
\nbecause the sender needs to be whitelisted). A typical
\nexample of an SMTP Error 550 return message by an
\nanti-spam firewall might be :
\n240.240.240.240 does not like recipient.
\nRemote host said: 550-Verification failed for
\nJohn.Doe@YourDomain.com
\n550-Previous (cached) callout verification failure
\n550 Sender verify failed
\nGiving up on 240.240.240.240.
\n————–
\nSMTP Error 550 will also be returned if the user’s
\nmailbox is not local and Mail Relay is not enabled, or
\nthe sending address is invalid (the latter is a way, by the
\nremote server, to control spam).
\n————–
\nOther situations of SMTP Error 550 include sending mail
\nto recipients outside of your domain where this is not
\nallowed.
\n————–
\nSMTP Error 550 is also returned when you are attempting
\nto send through a server which requires SMTP
\nauthentication and you have not supplied credentials (ie.
\nyour mail server, or email program, is attempting to send
\nwithout SMTP authentication)
\n————–
\nYet another set of circumstances where an SMTP error
\n550 might be issued include an incorrect From address
\nwhen used with an ISP where you can send mail only if
\nthe From address is from a domain that they host for
\nyou (at the time of writing, September 2008, British
\nTelecom in the UK is such an ISP – you have to notify
\nthem through a lengthy, ridiculous, and almost soul
\ndestroying procedure, involving proving that you own the
\ndomain, for them to allow you to send emails from a
\ndomain name that they do not host for you).
\n————–
\nAnother case of SMTP Error 550 is when the recipient’s
\nserver is down (or cannot receive mail at this time) and
\nthe ISP’s servers will retry periodically for a limited amount
\nof time (this is often accompanied by a return mail from
\nyour ISP informing the sender of the email of just that
\nsituation).
\n————–
\nAnother case of SMTP Error 550 is when the recipient’s
\nserver requires you to make a change to the To part of
\nyour email to achieve successful delivery of the email
\n(some organizations configure their receiving mail servers
\nin this way when they have changed their domain name
\nand want to force the senders to update his address books
\n– for example, My-Great-Company.com has changed its
\ndomain to MyGreatCompany.com and you are still using
\nthe old domain name).
\n————–
\nYet another set of circumstances when the SMTP Error
\n550 is received is when the recipient’s mailbox has
\nbeen suspended. For instance, the QMAIL SMTP mail
\nprogram has an endearing way of telling you about a
\nmailbox that has been suspended : “I’m afraid I wasn’t
\nable to deliver your message to the following addresses.
\nThis is a permanent error; I’ve given up. Sorry it didn’t work
\nout. <email-address@email-domain>: <ip-address-ofremote-
\nserver> does not like recipient. Remote host said:
\n550 [SUSPEND] Mailbox currently suspended – Please
\ncontact correspondent directly.”.
\n————–
\nAnother circumstance of an SMTP Error 550 is when the
\nrecipient’s mailbox has been disabled. The typical
\nreasons for this are the mailbox being full (the user needs
\nto delete messages before new ones will be accepted) or
\nthe user not having paid a bill. An example of the reply
\nyou will receive is : “550 mailbox temporarily disabled”
\n551 – User not local or
\ninvalid address –
\nRelay denied.
\n(also called SMTP Error 5.5.1)
\nSMTP Error 551 : If neither the sending mail address nor
\nthe recipient’s address are locally hosted by the server,
\nthen the ISP’s servers may refuse to relay the message
\non.
\nSome ISPs implement this restriction to thwart spammers.
\nIn our view, here at AnswersThatWork, this is a lazy and
\nincompetent method of fighting spam as most of the time it
\ndoes nothing but inconvenience no-one other than the
\nISP’s vast majority of considerate and law abiding users.
\nIn our experience this usually goes hand in hand with
\nbarely competent technical support. At the time of writing,
\n14-Sep-2008, a typical culprit for this is BT, British
\nTelecom, in the UK. The way in which it manifests itself is
\nas follows : you have a domain that is hosted by
\nCrystalTech.com but your ISP is DodgyISP.com and
\nyou try to send emails from your domain to
\nWhatANiceBunchOfPeopleYouAre@yahoo.usa.
\nNeither your domain nor Yahoo.usa are hosted by
\nDodgyISP.com, as a result your email is not accepted by
\nDodgyISP’s mail servers and your mail server is returned
\nan SMTP Error 551. To correct the problem you have to
\ncall DodgyISP.com and ask them to enter your domain
\nname as an allowed sender.
\n552 – Requested mail
\nactions aborted –
\nExceeded storage
\nallocation.
\n(also called SMTP Error 5.5.2)
\nSMTP Error 552 : The recipient’s mailbox has reached its
\nmaximum allowed size (this is often accompanied by a
\nreturn mail from your ISP or mail server informing the
\nsender of the email of just that situation).
\nExample : “552 sorry, mailbox Alan@ThisCompany.com
\nis over quota temporarily (#5.1.1)”.
\n————–
\nSome mail servers have extended the scope of SMTP
\nReply Code 552 by also including errors where the size of
\nthe incoming message exceeds the size limit specified by
\nthe Network Administrator, as in, for example, “SMTP
\nError 552 5.2.3 Message size exceeds fixed maximum
\nmessage size (7000000)”, which effectively says that the
\nincoming message was larger than the 7MB limit
\n(7,000,000 bytes) set by the Network Administrator of the
\nrecipient’s mail server.
\n553 – Requested action not
\ntaken – Mailbox name
\ninvalid.
\n(also called SMTP Error 5.5.3)
\nSMTP Error 553 : There is an invalid email address in the
\n“To”, “CC”, or “BCC” field of the email message.
\nHere is a typical SMTP Error 553 response :
\n“Hi. This is the QMAIL-send program at <ip-address>. I’m
\nafraid I wasn’t able to deliver your message to the following
\naddresses. This is a permanent error; I’ve given up. Sorry
\nit didn’t work out. <Email-address-you’re-sending-to> :
\n<remote-mail-server-ip> does not like recipient. Remote
\nhost said: 553 5.3.0 <Email-address-you’re-sending-to>.
\nAddressee unknown. Giving up.”.
\n————–
\nSMTP Status 553 is also sometimes returned by an ISP
\nmail server. When this happens this is almost always
\nbecause you are trying to send through a specific ISP’s
\nSMTP server and yet you are not connected to the Internet
\nthrough that ISP, e.g. you are connected to the Internet
\nthrough a Comcast broadband connection but your email
\nprogram (Outlook Express, Windows Mail, …) is configured
\nto send emails through the SMTP server of Tiscali. A
\ntypical such error message might be : “553 sorry, relaying
\ndenied from your location”.
\n554 – Transaction failed.
\nNowadays SMTP
\nstatus 554 is in most
\ncases returned when
\nthe recipient server
\nbelieves your email is
\nspam or your IP
\naddress or ISP server
\nhas been blacklisted
\non one or more
\nSMTP Error 554 : There was a permanent error trying to
\ncomplete the mail transaction which will not be resolved by
\nresending the message in its current form. Some change
\nto the message and\/or destination must be made for
\nsuccessful delivery.
\nFor instance, Yahoo often returns the following if the
\nrecipient email address does not exist on the Yahoo
\nsystems : “554 delivery error: This user doesn’t have a
\nYahoo.com account”. Another typical Yahoo SMTP Error
\n554 reply is : “554 delivery error: Sorry your message to
\nInternet blacklists.
\nor
\nWith Yahoo, on the
\nother hand, this
\nusually means the
\nemail address does
\nnot exist or has been
\ndisabled.
\n(also called SMTP Error 5.5.4)
\n<Email-Address> cannot be delivered. This account has
\nbeen disabled or discontinued”.
\n————–
\nIn most cases, however, a recipient mail server will return
\nan SMTP REPLY 554 when its anti-spam firewall does
\nnot like the sender’s email address, or the sender’s IP
\naddress, or the sender’s ISP server (because, for
\nexample, they are listed in an RBL) and where you will
\ntherefore either need to have the sender whitelist you in
\ntheir anti-spam program\/appliance, or, worse, you will need
\nto take steps to have either your IP address or your ISP’s
\nservers (if you send mail through your ISP) de-listed from
\none or more RBLs (RBL = Realtime Blackhole List – also
\ncalled Realtime Blacklist nowadays).
\nFor example, a 554 error returned by a Comcast server
\nmight look like this : “Username@comcast.net SMTP error
\nfrom remote mail server after initial connection : host
\nmx2.comcast.net :
\n554 IMTA11.emeryville.ca.mail.comcast.net <Your-server-
\nIP-address> was found on one or more DNSBLs, see
\nhttp:\/\/help.comcast.net\/content\/faq\/BL000010”, where
\nDNSBLs = DNS Blacklists. In this case, therefore, if you
\nget such a message back it is telling you your IP address,
\nor your ISP’s mail server is listed on one of the anti-spam
\nblacklist databases that Comcast uses to filter out spam on
\nincoming emails to Comcast mailboxes – click the link
\nprovided in the error message to see how you may be able
\nto un-blacklist yourself as far as Comcast is concerned.
\nHere is another example from the OZEMAIL ISP in
\nAustralia, “SMTP error from remote mail server after initial
\nconnection to host mx1.ozemail.com.au :
\n554 filter.ozemail.com.au” – not very informative, as you
\ncan see, but the name of the server returning the SMTP
\nreply 554 is what gives this away as OZEMAIL’s anti-spam
\nnot liking you : filter.ozemail.com.au. “Filter” in the
\nname of a recipient server is almost always an indication
\nthat that server is an anti-spam and antivirus server.
\nNote that SMTP Error 554 can also often be buried in the
\nmiddle of SMTP Error 550 errors. Here is an example of a
\nrecipient mail server returning an SMTP Error 554 because
\nits Barracuda anti-spam firewall appliance rejected the
\nemail (the cause, as shown below, is Barracuda
\nReputation which means your IP address or your ISP’s
\nserver is blacklisted on Barracuda’s RBL) :
\n240.240.240.240 does not like recipient.
\nRemote host said: 550-Verification failed for
\nJohn.Doe@YourDomain.com
\n550-Called: 250.250.250.250
\n550-Sent: RCPT TO:John.Doe@YourDomain.com
\n550-Response:
\n554 : Service unavailable; Client host
\n[server11.virgohosting.net] blocked using Barracuda
\nReputation;
\nhttp:\/\/recipientdomain.barracudacentral.com\/q.cgi?ip=230.
\n230.230.230
\n550 Sender verify failed
\nGiving up on 240.240.240.240
\nThe following addresses had
\npermanent delivery errors
\n“The following addresses had permanent delivery
\nerrors” \/ “The following address had permanent
\ndelivery errors” : Either of these sentences are usually
\nfollowed by one or more email address(es).
\nThe error message is effectively saying that the email
\naddresses listed do not exist, or no longer exist (if you
\nused to be able to email to them successfully). You need
\nto get the sender to verbally verify with the recipient what
\nhis\/her new email address is.<\/p>\n","protected":false},"excerpt":{"rendered":"
SMTP Status Codes What the message may mean 101 – Cannot open connection (also called SMTP Error 1.0.1) SMTP Error 101 : Typically your SMTP server or email program is unable to even start an SMTP session. Typical replies will be “SMTP Error 101, Error<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"open","ping_status":"open","template":"","meta":{"footnotes":""},"_links":{"self":[{"href":"https:\/\/mailchita.com\/wp-json\/wp\/v2\/pages\/24"}],"collection":[{"href":"https:\/\/mailchita.com\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/mailchita.com\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/mailchita.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mailchita.com\/wp-json\/wp\/v2\/comments?post=24"}],"version-history":[{"count":1,"href":"https:\/\/mailchita.com\/wp-json\/wp\/v2\/pages\/24\/revisions"}],"predecessor-version":[{"id":25,"href":"https:\/\/mailchita.com\/wp-json\/wp\/v2\/pages\/24\/revisions\/25"}],"wp:attachment":[{"href":"https:\/\/mailchita.com\/wp-json\/wp\/v2\/media?parent=24"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}