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Email Server Status Codes

SMTP Status Codes What the message may mean
101 - Cannot open
(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 opening connection"
or "SMTP Error 101, cannot open SMTP stream".
All SMTP Error 101 errors usually point to a configuration
problem, such as an incorrectly spelt SMTP server, or an
IP address that does not exist, or an SMTP port that does
not exist or which the recipient will not accept SMTP
connections on, or some other process is already using the
default SMTP port, port 25.

211 - System Status
message or System
Help Reply
(also called SMTP Error 2.1.1)
SMTP Error 211 : SMTP status 211 prefaces a message
about the Mail Server status or a System Help reply to the
user requesting help information. You might for example
issue a command to the mail server to display a list of
commands you can use and the server replies with an
SMTP Reply 211 followed by the list you requested.

214 - Help Reply message (also called SMTP Error 2.1.4)
SMTP Error 214 : SMTP status 214 is usually in reply to
the "HELP" command. It displays information about the
server, usually a URL to the FAQ page of the SMTP
software running on the server. As a result this "error" is
normally called a reply, as in SMTP Reply 214.

220 - <Server Name> service is running (also called SMTP Error 2.2.0)
SMTP Status 220 : This is normally the first message you
will get back from the server. It means the mail service is
running (ie. your mail server is running). It will normally
contain a welcome message and/or the title of the SMTP
software and, sometimes, the version number of the mail
server software. SMTP Reply 220 is effectively a "Hi
There, I have just this second finished starting up - I
am ready to go and at your command" informational

221 - The domain service is closing the transmission channel (also called SMTP Error 2.2.1)
SMTP Error 221 : The server is ending the mail session -
it is closing the conversation with the ISP as it has no more
mail to send in this sending session.
SMTP Status 221 is often misconstrued as an error
condition, when it is in fact nothing of the sort. The mail
server is simply telling you that it has processed everything
it was given in this particular session, and it is now going
back into waiting mode.
Because SMTP status 221 is often misinterpreted, with
some mail servers the Network Administrators have
changed the default text of SMTP Reply 221 to something
more meaningful and less alarming. For example, a typical
SMTP reply 221 might say "221 Goodbye" or
"221 Closing connection", or the most irritating one we've
seen "221 Bye", Arrrgghh - can you blame anyone for
thinking there might be a problem ? Of course not ! So
some Network Administrators are these days being quite
imaginative by changing the default text of SMTP reply 221
to more user friendly messages like : "221 Thank you for
your business" (I love that one!), or "221 All messages
processed successfully in this session, SMTP connection
is closing".

250 - Requested mail
action OK completed
(also called SMTP Error 2.5.0)
SMTP Status 250 : The mail server has successfully
delivered the message! This is the best SMTP reply (250)
to receive - your message has been accepted and
transmitted OK ! J Yippee.
250 is effectively a status code rather than an error code -
there is no such thing as an SMTP error 250.
251 - User not local will
(also called SMTP Error 2.5.1)
SMTP Status 251 : The email account is not local to the
ISP server but the ISP server will accept the email and will
forward it (the server will RELAY your message, this is the
most common action for ISP Mail servers - the recipient
will see your ISP in the mail header as one of the first hops
on the way to the recipient's email system).
SMTP Error 251 is therefore more of an informational
message for technicians tracking how a message reached
its destination.

252 - Cannot VRFY (verify)
the user - the server
will accept the
message and attempt
to deliver it
(also called SMTP Error 2.5.2)
SMTP Status 252 : The user account appears to be valid
but could not be verified, however the server will try do
deliver the message.
There are sometimes circumstances where an email
address appears to be valid but cannot be verified as
definitely valid during the SMTP session between the
sending server (your server) and the next server to accept
your message. This can happen for example in very large
corporation where the first email receiving server might
only be an email exchanger server, a gateway server to
the eventual server which holds the user mailboxes and
which can verify if the intended recipient exists in that
organization. When this happens the gateway server will
reply with an SMTP Error 252 telling your sending server
that it cannot verify the user part of the email address, that
the domain part is OK, and that it will forward your email to
a server which can do the checking and eventually deliver
to the user mailbox if it exists.

354 - Start mail input end
with <CRLF>.<CRLF>,
or, as a less cryptic
description - "FROM
and TO information
received, now please
provide message
body and mark its
end with
(also called SMTP Error 3.5.4)
SMTP Error 354 : This is normally in response to the
DATA command. The server has received the From and
To information and is now asking for the "Message
Body", the main part of the message which should be
ended by two blank lines separated by a dot (period).
Therefore, on receiving an SMTP Reply 354 the sending
server should send the body of the message to the
receiving server and indicate the end of the message body
with <CRLF>.<CRLF> (note the full stop between the two

421 - <Server name>
Service not available
- the sending email
program should try
again later
(also called SMTP Error 4.2.1)
SMTP Error 421 : The Mail transfer service is unavailable
because of a transient event. SMTP reply 451 can be
caused by many things but generally indicates that the mail
server which returns this status code is currently
unavailable but may be available later.
For example, the server administrator may have stopped
the mail service to troubleshoot a problem, or the mail
server is right in the middle of rebooting, or the mail server
is currently processing too many incoming messages or
incoming requests, etc.... Note : "Mail Server" in this
case can be any of the mail servers on the message's
route - the sending server (your server), the ISP SMTP
server, or the recipient's mail server.
Clearly, if you repeatedly receive an SMTP status 421 then
the problem is no longer of a transient nature and you
need to investigate or inform the relevant network
administrator, ISP tech support, or the recipient.

422 - The recipient's
mailbox is over its
storage limit
(also called SMTP Error 4.2.2)
SMTP Error 422 : Either the recipient's mailbox is over its
storage limit or the message delivery directory (folder) on
the recipient's mail server is currently over a size limit
imposed by the Network Administrator (e.g. possibly as a
result of the mail server having been down for some time,
having been repaired, and currently in the process of
collecting thousands of queued up messages).

431 - The recipient's mail
server is experiencing
a Disk Full condition
(also called SMTP Error 4.3.1)
SMTP Error 431 : The recipient's mail server is
experiencing a Disk Full error condition, or an Out of
Memory (too many file handles) error condition (Microsoft

432 - The recipient's
Exchange Server
incoming mail queue
has been stopped
(also called SMTP Error 4.3.2)
SMTP Error 432 : This is an SMTP status response
specific to Microsoft Exchange Server. It indicates that the
recipient's mail queue on their Exchange Server has been
stopped (frozen), probably while the Network Administrator
troubleshoots some problem.

441 - The recipient's server
is not responding
(also called SMTP Error 4.4.1)
SMTP Error 441 : This is an error emanating from your
server indicating that the recipient's server is not
responding. Your server will automatically try again a
number of times - how many depends on how your server
has been configured.

442 - The connection was
dropped during
(also called SMTP Error 4.4.2)
SMTP Error 442 : Your server started delivering the
message but the connection was broken during
transmission. This may be an unusual transient error -
however, if it keeps happening you should investigate
possible problems with your server's network card, your
Internet routers, processes hogging the resources of your
server, and anything else which could result in a network
connection being broken.

446 - The maximum hop
count was exceeded
for the message
(also called SMTP Error 4.4.6)
SMTP Error 446 : The maximum hop count was
exceeded for your message. The most likely cause of this
error status code is that your message is looping internally
on your server, internally between two of your
organisation's servers, or, sometimes, looping between
your server and the recipient's server.

447 - Your outgoing
message timed out.
(also called SMTP Error 4.4.7)
SMTP Error 447 : Your outgoing message timed out
because of problems with the receiving server who
objected to your message. Typically there is a problem
with the message header (such as too many recipients, in
most cases, or a protocol timeout between the two

449 - Routing error
(also called SMTP Error 4.4.9)
SMTP Error 449 : This is a Microsoft Exchange Server
specific error code. As per Microsoft's documentation this
error code is returned when either of the following
conditions occurs : an SMTP connector is configured to
use DNS without a smart host and also uses a non-SMTP
address space (e.g. X.400), or A message was sent to a
recipient who was identified as a member of a routing
group that was deleted.
Microsoft recommends using the WinRoute tool to
troubleshoot this error (Microsoft Knowledgebase article

450 - Requested action not
taken - The mailbox
was unavailable at the
remote end. A
secondary SMTP
error code may follow
"450" to refine the
reason for the failure
to transmit the
message, e.g.
"SMTP Error 450
(also called SMTP Error 4.5.0)
SMTP Error 450 : The server could not access the
mailbox to deliver the message. This could be caused by
a process on the remote server tidying up the mailbox, or
the remote mailbox could be corrupt, or the remote mailbox
may be stored on another server which is currently offline,
or the network connection went down while sending, or the
remote mail server does not want to accept mail from your
server for some reason (IP address, blacklisting, etc..).
In general SMTP Error 450 is a transient error at the
remote end (the destination), or at one of the servers
en route to the remote end, and should induce your
mail server to retry after it's preset retry interval.
Example of an SMTP Error 450 reply message : "450
Please try again later".
SMTP Error 450 is often followed by a second SMTP error
code to refine the reason for the email not reaching its
destination. For example : "SMTP Error 450 5.2.3 Msg
Size greater than allowed by Remote Host". When that is
the case and If the error message is not as clearly worded
as in this example, then simply search this document for
the secondary error code. In this case searching this
document for SMTP Error 523 or SMTP Error 5.2.3 would
yield an explanation identical to the wording above.

451 - Requested action
aborted - Local error
in processing.
(also called SMTP Error 4.5.1)
SMTP Error 451 : The action has been aborted by the
ISP's server. "Local" refers to the ISP's server. This
error is usually due to overloading at the ISP from too
many messages or transient failures. Typically some
[hopefully] temporary event prevents the successful
sending of the message. The next attempt to send by your
server may prove successful.
If this error keeps occurring to the point that it has
effectively lost its transient nature and has become
..... frequent (!!), then the problem is at your end and
you should check your own mail server (if you email out of
a corporate network), communications on your side (router,
server network card), or inform your ISP if your mail server
relays through your ISP or if you are a home user emailing
out through Outlook, Outlook Express, Windows Mail, or
similar email program.
Example of typical SMTP Error 451 return messages :
"SMTP error 451 Unable to complete command, DNS not
available or timed out" or "451 Domain of sender address
does not resolve" or "451 Error getting LDAP results in

452 - Requested action not
taken - Insufficient
(also called SMTP Error 4.5.2)
SMTP Error 452 : The ISP server's disk system has run
out of storage space, so the action had to be cancelled.
Unless you are with an ISP which is so slack that they
have not implemented Disk Full Alerts, this error usually
indicates that your ISP's mail server is overloaded from too
many messages. This can happen even to the best ISPs
when, for example, there have been problems and none of
the ISP's customers could send mail; as soon as the
problems are fixed there is almost always a situation where
thousands of users and organizations are trying to send
mail all at the same time, and those numbers can
occasionally result in the ISP's mail servers' hard disks
temporarily filling up, with SMTP Error 452 being the result.
The next attempt to send by your server may prove
SMTP Error 452 : Most ISPs mail servers impose a
maximum number of concurrent connections that client's
mail servers can attempt to make, and they usually also
have a limit on the number of messages that are sent per
connection. With business customers these maximums
are rarely reached, if ever. Nevertheless, If you have a lot
of messages queued up, for example as a result of the
connection to your ISP going down for a significant amount
of time (and you have hundreds of users in your
organization, or it happened just as you were about to
send that large mailshot!), there could be a situation where
the output of messages from your server goes over the
maximum number of messages per connection allowed by
your ISP. This is another case where the ISP's server may
issue a 452 SMTP error. As above, the next attempt to
send by your server may prove successful.
SMTP Error 452 : This error can also be indicative of a
problem on your own mail server. Here is an example of
an SMTP 452 error : ""452 Out of memory"

465 - Code Page
unavailable on the
recipient server
(also called SMTP Error 4.6.5)
SMTP Error 465 : This is an Exchange Server-specific
error code. This error is returned by the recipient's server
if the incoming email specifies a Code Page that is not
installed on the recipient's server, normally because not all
language files were installed on the server during either the
installation of Windows or of Exchange Server.

471 - This is a local error
with the sending
server and is often
followed with "Please
try again later"
(also called SMTP Error 4.7.1)
SMTP Error 471 : This is always a local error with your
own mail server. SMTP Error 471 (or 4.7.1) is usually
tagged onto a primary SMTP error code, for example
"SMTP Error 450 4.7.1", or "SMTP Error 451 4.7.1", or
"SMTP Error 550 4.7.1". In all the cases that we have
seen SMTP Error 471 is usually caused by anti-spam or
virus scanning software on your server (the sending
server) getting into problems through a bug in the software,
or because of a bad automatic update from the
antivirus/anti-spam manufacturer, because of lack of
memory on your server, or because of hard disk problems.

500 - Syntax error
command not
(also called SMTP Error 5.0.0)
SMTP Error 500 : The last command sent by your server
was not recognized as a valid SMTP or ESMTP command,
or is not formatted in the way the server expected. This
includes situations where the command is too long.
Note that commands that are recognized, but not
implemented, are handled by different status messages
(see 502 and 504).

501 - Syntax error in
parameters or
arguments (e.g.
invalid email address)
Can sometimes also
be indicative of
(also called SMTP Error 5.0.1)
SMTP Error 501 : The command was correct and
recognised, but the parameters (the arguments, e.g. email
address) were not valid.
For example, the following email address will definitely give
an SMTP Error 501 with most mail servers,
happy\, as "\" is not allowed in email
addresses, which makes this email address invalid.
In the vast majority of cases SMTP Error 501 is caused
by invalid email addresses. For example, a typical return
error message might be : "<remote-server-ip-address>
does not like recipient. Remote host said: 501 Invalid
In cases where the error is not caused by an invalid email
address, an SMTP Error 501, particularly if repeated, can
be indicative of communications problems, such as a noisy
line, intermittent drops in network connections, etc...

502 - Command not
(also called SMTP Error 5.0.2)
SMTP Error 502 : The command or function issued by
your mail server is valid but has not been activated
(typically, it is not supported on this particular server).

503 - Bad sequence of
This mail server
(also called SMTP Error 5.0.3)
SMTP Error 503 : In the original standards SMTP Status
503 indicates that the commands have been sent in the
wrong order, for example your mail server has sent the
"Hello" command before sending the "Mail" command.
This can often be caused by a drop in network connection
just as your server was sending a command, resulting in
the ISP's server not receiving it and consequently not
understanding the command that followed it.
Note : this error, particularly if repeated, can be indicative
of communications problems, such as a noisy line,
intermittent drops in network connections, etc...
SMTP Reply Code 503 is nowadays more often an
indicator that the SMTP server you are trying to use
requires authentication and you tried to send a message
without authentication (username + password). This
SMTP Error 503 is permanent in that the SMTP server, will
not log any errors in its log and it will not retry - you will
have to resend the email using authentication. Example of
such an error : "SMTP Error (state 13): 503 This mail
server requires authentication when attempting to send to
a non-local e-mail address. Please check your mail client
settings or contact your administrator to verify that the
domain or address is defined for this server.".

504 - Command parameter
not implemented.
(also called SMTP Error 5.0.4)
SMTP Error 504 : The command and parameter are both
valid, but the parameter is not implemented on the ISP
server, or an additional parameter or action is missing.
For example, an often encountered SMTP Error 504 is :
"504 Need to authenticate first".

510 - Bad Email Address
(also called SMTP Error 5.1.0)
SMTP Error 510 : Bad email address. This status code
is generated by the sender's local mail server.
If the email was addressed internally, then it means that
the addressee, as written in the email's TO, CC, or BCC
fields, does not exist in your organization's email system.
If the email was addressed externally, then the recipient's
email address was misspelt.

511 - Bad Email Address
(also called SMTP Error 5.1.1)
SMTP Error 511 : Bad email address. This error is
similar to error 510 and as with error 510, this status code
is generated by the sender's local mail server.
If the email was addressed internally, then it means that
the addressee, as written in the email's TO, CC, or BCC
fields, does not exist in your organization's email system.
If the email was addressed externally, then the recipient's
email address was misspelt.

512 - The host server for
the recipient's
domain name cannot
be found (DNS error)
(also called SMTP Error 5.1.2)
SMTP Error 512 : This SMTP reply code is received
when one of the servers on the way to the destination is
unable to resolve the domain name of a recipient email
address. Said differently : one of the servers on the way
to the destination, including your server or your ISP, has a
DNS problem or, possibly correctly, does not like one of
the email addresses in the message's TO, CC, and BCC
The first check you should perform to resolve a 5.1.2 reply
code is to check all the recipient email addresses for
incorrect domain names (misspelt domain names, or,
maybe, totally non-existent domain names) - remember,
error code 512 is very specifically an error with the
domain name of one of the recipient email addresses.
You can call the recipient(s) or use the WHOIS tool of The
Ultimate Troubleshooter. If all the recipient email
addresses check out as regards the domain part of the
email addresses, then one of the servers on the way to the
recipient(s) has DNS problems - usually this will be one of
the first 2 servers in the chain, your own mail server (or
your network) or your ISP's mail server.
Examples of typical SMTP error 512 messages : "5.1.2 -
Bad destination host 'DNS Hard Error looking up domain",
or "SMTP Error 550 5.1.2 Host unknown - host cannot be
found", or how about this fantastically informative error
message "5.1.2 The message could not be delivered
because the recipient's destination email system is
unknown or invalid. Please check the address and try
again, or contact your system administrator to verify
connectivity to the email system of the recipient.".
In summary : most SMTP error 512 conditions are
caused by misspellings of the domain name part of a
recipient email address. However, with the proliferation
of spam, error 512 is also often encountered by automatic
"out-of-office" replies to junk mail because the domain
names used by junk mail are often bogus domain names.
513 - Address type is
incorrect (most mail
Relaying denied or
required (a small
percentage of mail
(also called SMTP Error 5.1.3)
SMTP Error 513 : This status code (from the sender's
mail server) is usually symptomatic, in an Exchange +
Outlook environment, of the user's Outlook Contacts
having been imported from another system or PST and
where some of the addresses are not defined correctly.
Or, in any environment it is simply that the end-user simply
did enter the email address completely wrongly, such as
copying it from a website and not replacing "at" with "@",
e.g. : (which should have been, or" (",
quotes, is not allowed in email addresses and is often
included in error as a result of copying and pasting an
email from somewhere).
The user should check all the recipient addresses in the
email, including those that were inserted from Contacts.
Note : the SMTP reply code 5.1.3 is often a secondary
reply code. Some mail servers, for example, might reply
"SMTP error 501 5.1.3 Invalid address", or "SMTP error
553 5.1.3 User address required !", or "SMTP error 501
5.1.3 Bad recipient address syntax", or "SMTP error 513
Relaying Denied - Can not send e-mails to some
addresses", or this excellently informational Exchange
Server 2007 error (the whole error message is in green
below) :
"SMTP error 550 5.1.3 STOREDRV.Submit; invalid
recipient address.
Delivery has failed to these recipients or distribution lists:
The format of the recipient's e-mail address isn't valid. A
valid address looks like this:
Microsoft Exchange will not try to redeliver this message
for you. Please check the e-mail address and try sending
the message again, or provide the following diagnostic text
to your system administrator.
5.1.3: The format of the recipient e-mail address is not
valid. Valid SMTP e-mail addresses can contain only
letters, numbers, hyphens, periods, and only one @
symbol. Troubleshooting: Verify that the SMTP address of
the recipient is formatted correctly and resend the
SMTP Error 513 is also used by a small percentage of
mail servers to indicate a completely different error, namely
that you need to authenticate to the mail server before
being able to send your message (SMTP authentication).
A typical error message might be : "SMTP error 553
Authentication is required to send mail as".
In such cases you simply need to configure your mail
server, or your email program to send emails with SMTP

523 - The Recipient's
mailbox cannot
receive messages
this big
(also called SMTP Error 5.2.3)
SMTP Status 523 : This error will be received when the
total size of the message you have sent (ie: message + all
of its attachments) exceeds the size limits on the
Recipient's server. Many companies implement the good
practice of configuring their servers with limits on the size
of emails they can receive to prevent their systems running
out of space as a result of a spam attack where the spam
emails contain large attachments, or as a result of valid but
not very technically savvy senders sending enormous
scans (through not knowing that scanning at 1200dpi
rather than the usually perfectly usable and acceptable
300dpi, will create humongous attachments).
Check the size of the email you sent, and, specifically, the
size of the attachments you included, and consider splitting
your email into smaller emails. If that does not work, check
with the Recipient the maximum size of email they can
receive, and if that is still prohibitive then consider FTP
arrangements between you and the recipient.
SMTP Error 523 is often a secondary SMTP error code
rather than a primary error code, as in the following
examples : "SMTP Error 450 5.2.3 Message Size greater
than allowed by Remote Host" or "SMTP Error 552 5.2.3
Data size exceeds maximum permitted" or "SMTP Error
552 5.2.3 Message exceeds maximum fixed size", and so
on ....

550 - Requested actions
not taken as the
mailbox is
(also called SMTP Error 5.5.0)
SMTP Error 550 : This response can be caused by quite
a few situations.
SMTP Error 550 will be returned by many servers If the
recipient email address simply does not exist on the
remote side (you will often get "550 Invalid recipient" or
"550 User account is unavailable" or "<ip-address-ofremote-
server> does not like recipient - 550 Address
rejected" or "550 No such user here" or "550 Not our
Customer" or "550 Account not available" or "Remote
host said : 550 -, this
THISCOMPANY.COM Mailbox Does Not Exist - Giving
up"). In this case the sender of the email needs to contact
the recipient verbally to get the correct email address.
SMTP Error 550 will sometimes also be returned by the
recipient's anti-spam firewall if, for example, the
anti-spam firewall does not like the sender (typically
because the sender needs to be whitelisted). A typical
example of an SMTP Error 550 return message by an
anti-spam firewall might be : does not like recipient.
Remote host said: 550-Verification failed for
550-Previous (cached) callout verification failure
550 Sender verify failed
Giving up on
SMTP Error 550 will also be returned if the user's
mailbox is not local and Mail Relay is not enabled, or
the sending address is invalid (the latter is a way, by the
remote server, to control spam).
Other situations of SMTP Error 550 include sending mail
to recipients outside of your domain where this is not
SMTP Error 550 is also returned when you are attempting
to send through a server which requires SMTP
authentication and you have not supplied credentials (ie.
your mail server, or email program, is attempting to send
without SMTP authentication)
Yet another set of circumstances where an SMTP error
550 might be issued include an incorrect From address
when used with an ISP where you can send mail only if
the From address is from a domain that they host for
you (at the time of writing, September 2008, British
Telecom in the UK is such an ISP - you have to notify
them through a lengthy, ridiculous, and almost soul
destroying procedure, involving proving that you own the
domain, for them to allow you to send emails from a
domain name that they do not host for you).
Another case of SMTP Error 550 is when the recipient's
server is down (or cannot receive mail at this time) and
the ISP's servers will retry periodically for a limited amount
of time (this is often accompanied by a return mail from
your ISP informing the sender of the email of just that
Another case of SMTP Error 550 is when the recipient's
server requires you to make a change to the To part of
your email to achieve successful delivery of the email
(some organizations configure their receiving mail servers
in this way when they have changed their domain name
and want to force the senders to update his address books
- for example, has changed its
domain to and you are still using
the old domain name).
Yet another set of circumstances when the SMTP Error
550 is received is when the recipient's mailbox has
been suspended. For instance, the QMAIL SMTP mail
program has an endearing way of telling you about a
mailbox that has been suspended : "I'm afraid I wasn't
able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work
out. <email-address@email-domain>: <ip-address-ofremote-
server> does not like recipient. Remote host said:
550 [SUSPEND] Mailbox currently suspended - Please
contact correspondent directly.".
Another circumstance of an SMTP Error 550 is when the
recipient's mailbox has been disabled. The typical
reasons for this are the mailbox being full (the user needs
to delete messages before new ones will be accepted) or
the user not having paid a bill. An example of the reply
you will receive is : "550 mailbox temporarily disabled"
551 - User not local or
invalid address -
Relay denied.
(also called SMTP Error 5.5.1)
SMTP Error 551 : If neither the sending mail address nor
the recipient's address are locally hosted by the server,
then the ISP's servers may refuse to relay the message
Some ISPs implement this restriction to thwart spammers.
In our view, here at AnswersThatWork, this is a lazy and
incompetent method of fighting spam as most of the time it
does nothing but inconvenience no-one other than the
ISP's vast majority of considerate and law abiding users.
In our experience this usually goes hand in hand with
barely competent technical support. At the time of writing,
14-Sep-2008, a typical culprit for this is BT, British
Telecom, in the UK. The way in which it manifests itself is
as follows : you have a domain that is hosted by but your ISP is and
you try to send emails from your domain to
Neither your domain nor Yahoo.usa are hosted by, as a result your email is not accepted by
DodgyISP's mail servers and your mail server is returned
an SMTP Error 551. To correct the problem you have to
call and ask them to enter your domain
name as an allowed sender.
552 - Requested mail
actions aborted -
Exceeded storage
(also called SMTP Error 5.5.2)
SMTP Error 552 : The recipient's mailbox has reached its
maximum allowed size (this is often accompanied by a
return mail from your ISP or mail server informing the
sender of the email of just that situation).
Example : "552 sorry, mailbox
is over quota temporarily (#5.1.1)".
Some mail servers have extended the scope of SMTP
Reply Code 552 by also including errors where the size of
the incoming message exceeds the size limit specified by
the Network Administrator, as in, for example, "SMTP
Error 552 5.2.3 Message size exceeds fixed maximum
message size (7000000)", which effectively says that the
incoming message was larger than the 7MB limit
(7,000,000 bytes) set by the Network Administrator of the
recipient's mail server.
553 - Requested action not
taken - Mailbox name
(also called SMTP Error 5.5.3)
SMTP Error 553 : There is an invalid email address in the
"To", "CC", or "BCC" field of the email message.
Here is a typical SMTP Error 553 response :
"Hi. This is the QMAIL-send program at <ip-address>. I'm
afraid I wasn't able to deliver your message to the following
addresses. This is a permanent error; I've given up. Sorry
it didn't work out. <Email-address-you're-sending-to> :
<remote-mail-server-ip> does not like recipient. Remote
host said: 553 5.3.0 <Email-address-you're-sending-to>.
Addressee unknown. Giving up.".
SMTP Status 553 is also sometimes returned by an ISP
mail server. When this happens this is almost always
because you are trying to send through a specific ISP's
SMTP server and yet you are not connected to the Internet
through that ISP, e.g. you are connected to the Internet
through a Comcast broadband connection but your email
program (Outlook Express, Windows Mail, ...) is configured
to send emails through the SMTP server of Tiscali. A
typical such error message might be : "553 sorry, relaying
denied from your location".

554 - Transaction failed.
Nowadays SMTP
status 554 is in most
cases returned when
the recipient server
believes your email is
spam or your IP
address or ISP server
has been blacklisted
on one or more
SMTP Error 554 : There was a permanent error trying to
complete the mail transaction which will not be resolved by
resending the message in its current form. Some change
to the message and/or destination must be made for
successful delivery.
For instance, Yahoo often returns the following if the
recipient email address does not exist on the Yahoo
systems : "554 delivery error: This user doesn't have a account". Another typical Yahoo SMTP Error
554 reply is : "554 delivery error: Sorry your message to
Internet blacklists.
With Yahoo, on the
other hand, this
usually means the
email address does
not exist or has been
(also called SMTP Error 5.5.4)
<Email-Address> cannot be delivered. This account has
been disabled or discontinued".
In most cases, however, a recipient mail server will return
an SMTP REPLY 554 when its anti-spam firewall does
not like the sender's email address, or the sender's IP
address, or the sender's ISP server (because, for
example, they are listed in an RBL) and where you will
therefore either need to have the sender whitelist you in
their anti-spam program/appliance, or, worse, you will need
to take steps to have either your IP address or your ISP's
servers (if you send mail through your ISP) de-listed from
one or more RBLs (RBL = Realtime Blackhole List - also
called Realtime Blacklist nowadays).
For example, a 554 error returned by a Comcast server
might look like this : " SMTP error
from remote mail server after initial connection : host :
554 <Your-server-
IP-address> was found on one or more DNSBLs, see", where
DNSBLs = DNS Blacklists. In this case, therefore, if you
get such a message back it is telling you your IP address,
or your ISP's mail server is listed on one of the anti-spam
blacklist databases that Comcast uses to filter out spam on
incoming emails to Comcast mailboxes - click the link
provided in the error message to see how you may be able
to un-blacklist yourself as far as Comcast is concerned.
Here is another example from the OZEMAIL ISP in
Australia, "SMTP error from remote mail server after initial
connection to host :
554" - not very informative, as you
can see, but the name of the server returning the SMTP
reply 554 is what gives this away as OZEMAIL's anti-spam
not liking you : "Filter" in the
name of a recipient server is almost always an indication
that that server is an anti-spam and antivirus server.
Note that SMTP Error 554 can also often be buried in the
middle of SMTP Error 550 errors. Here is an example of a
recipient mail server returning an SMTP Error 554 because
its Barracuda anti-spam firewall appliance rejected the
email (the cause, as shown below, is Barracuda
Reputation which means your IP address or your ISP's
server is blacklisted on Barracuda's RBL) : does not like recipient.
Remote host said: 550-Verification failed for
550-Sent: RCPT
554 : Service unavailable; Client host
[] blocked using Barracuda
550 Sender verify failed
Giving up on
The following addresses had
permanent delivery errors
"The following addresses had permanent delivery
errors" / "The following address had permanent
delivery errors" : Either of these sentences are usually
followed by one or more email address(es).
The error message is effectively saying that the email
addresses listed do not exist, or no longer exist (if you
used to be able to email to them successfully). You need
to get the sender to verbally verify with the recipient what
his/her new email address is.

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