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Bounce messages can be broken down into three groups. Look
for the error message that most closely matches the one you
received.
User Bounces
Temporary Problems likely to be fixed soon
Mailbox is full
The most common user problem is a full mailbox. Most
systems have a limit on how much email is allow to reside on
the server for each user, and once that limit is reached,
there is no room to accept new incoming mail. The following
are all examples of bounce messages caused by a full
mailbox:
<user@yahoo.com>: User is over the quota. You can try again later.
<user@ibm.net>: host in7.ibm.net said:
552 <user@ibm.net>... Mailbox is full
procmail: Mailbox limit exceeded while appending message
550 <user@codetel.net.do>... Can't create output
<user@hotmail.com>: host mail9.hotmail.com said:
552 Requested mail action aborted: exceeded storage allocation
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This error will stop as soon as the recipient makes
additional room in their mailbox (usually by removing old
messages from the server), so you should probably resend
your message a little later. However, especially with free
accounts, this message could actually mean the user no longer
checks the account; a good rule of thumb is if you continue
to receive this error for more than two weeks, it is likely
that the account is no longer in use.
Message exceeds size limit
<user1@home.com>: host mx-rr.home.com said:
552 Message size exceeds fixed maximum message size (5000000)
<user@yahoo.com>: host mx2.mail.yahoo.com said:
552 message size exceeds maximum message size
<user@bellsouth.net>: host mx01.mail.bellsouth.net said:
552 Message size exceeds fixed maximum message size: 5242880 bytes
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These errors mean that the size of the message,
including all headers, text and attachments, exceeds the
domain's maximum per-message size limit - essentially, that
your email is too big to be accepted. You should try to
reduce the size of the message, or try to split the email
into smaller parts and resend it.
Other types of errors that should be quickly fixed can
be caused by users misconfiguring their own email accounts.
For instance:
Improper forwarding causing mail loop:
554 Too many hops 27 (25 max): from <user@firstdomain.com>
via mail.firstdomain.com, to <sameuser@seconddomain.com>
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In general, a "too many hops" error indicates a
mail loop: the user has two accounts, forwarding to each
other, which creates an endless loop. A message sent a
Pobox account is forwarded to another mailbox; if that
account is set to forward to Pobox, then a mail loop
is created: mail goes from Pobox to the mailbox back to
Pobox back to the mailbox, et cetera, until the loop is
ascertained and the message returned to its sender.
Permanent Problems
The most common permanent user problem is, of course,
User Unknown. The account you are trying to mail no
longer exists - it may have been shut down, or you may have
misspelled the username or domain (make sure you check
bounce messages carefully). The following are all examples
of User Unknown messages:
<user@earthlink.net>: host condor.prod.itd.earthlink.net said:
550 <user@earthlink.net>... User unknown
<user@hotmail.com>: host mail7.hotmail.com said:
550 Requested action not taken: mailbox unavailable
<user@apc.net>: host mail.apc.net said:
550 5.1.1 <user@apc.net> is not a valid mailbox
<user@riviera.org.uk>:
Sorry, no mailbox here by that name. (#5.1.1)
<user@saccny.org>: host hhh.net said:
550 Invalid recipient <user@saccny.org>
The message that you sent was undeliverable to the following:
user@ashrosary.org (user not found)
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If you receive a user unknown bounce, and you have checked
to make sure the address is correct, the next thing you
should do is try to contact the person you were trying to
email by other means. Frequently, people are not aware that
they are bouncing email until someone else tells them.
Also, do not delete the bounce message. It can help the
user and their ISP resolve why they are bouncing mail more
quickly.
If you do not have other means to contact the
person who is bouncing mail, you probably have a dead email
address. Try mailing them one more time (preferably at
least a day later) in case it was a technical problem, but
after that, stop using that email address. If you run a
mailing list, and one of your subscribers starts bouncing
mail with this error, remove them from the list.
Domain
Bounces
Most of the time, when a domain has an email problem,
they learn about it very quickly from their users, and in
addition, it is relatively rare for an entire domain to
simply disappear, so most domain errors should be considered
temporary, and will likely be remedied soon -- resending
mail a little later is usually your best option.
Connection Timed Out / Connection Refused
<user@166.131.9.213>: connect to 166.131.9.213: Connection timed out |
A "connection refused," or "connection timed
out" message usually results from high volumes of mail
being processed at the time your message was received. This
could be due to the server receiving more mail then it is
used to, a external attack on a domain (such as a mailbomb)
or an internal setup problem, causing the domain's mail
servers to refuse connections or cut connections before a
message is fully sent. Mail exchangers are set up to only
accept as much mail as they can handle, so when problem is
resolved, you will be able to send your mail without
problem.
Domain Not Found
<sheabu@domain.com>: Name service error for domain domain.com:
Host not found, try again |
A "domain not found" error means that the domain
name to which you sent the message does not exist. Usually,
this means you misspelled the domain name, but it may
indicate a problem with the domain's record that prevents
the domain from being found. There is another Domain Not
Found error: "Sender Address Rejected: Domain Not
Found"; for more information, please see
Domain Not Found: Anti-Spam bounce below.
Relay Access Denied
Another domain error that can be due to either the sender's
or recipient's domain is a relay access denied error:
<recipient@yahoo.com> host wormwood.pobox.com said:
554 <recipient@yahoo.com>: Recipient Address rejected:
Relay access denied
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This error indicates that, somehow, a message intended for a
Yahoo.com address found its way to our wormwood.pobox.com
mail server, and since our server doesn't accept mail for
yahoo.com, the message was rejected. It is quite rare,
actually, to reach a completely incorrect mail server when
sending email to a domain, so if you receive this message,
the problem is usually a misconfiguration error with the
receiving domain (for example, if you receive notice that
mail sent to a Pobox user was rejected by a Pobox mail
server with this "Recipient Address rejected,"
error, this could indicate a problem with our mail servers,
since Pobox's mail servers obviously should accept email for
Pobox users. Or, it could indicate a problem where the
sender's system isn't looking the mail server up correctly).
Another reason for receiving this error is the possibility
that a domain has recently changed hosts, and while the
change has taken place, the new domain record has not yet
propagated fully, and your message reached the old hosting
company which no longer accepts mail for the leaving
domain. If you receive this error, try resending your
message twenty-four hours later.
Another Relay Access Denied error exists:
"Sender Address rejected: Relay Access
Denied"; this is actually an anti-spam bounce, so
please see Relay Access Denied: Anti-Spam
bounce below.
Anti-Spam Bounces
System administrators frequently set up their systems to
refuse mail from spammers, but since no spam filtering
system is perfect, your message may have been caught in the
spam block. Some of the most common:
Spam blocks
<user@sitcom.co.il>: host ntserver.sitcom.co.il refused to talk to me:
550 Permission denied
or contains a creative note, such as
<user@domain.net>: connect to domain.net:
550 Connection refused - we hate spammers! |
These errors mean that your provider's domain name (or
specifically, your email address) is explicitly listed as a
known spammer on a blacklist. This may be based on an
external service that provides blacklists of known spammers
to ISPs, or the administrator may have placed a block based
on a large volume of mail coming from your domain. Most of
the time, your email provider will need to contact the
system administrator to have the block removed, so you
should contact your provider immediately. Assuming that
your provider is, in fact, not a spamming service, they will
want to act quickly to get themselves removed from these
blacklists.
There are two other anti-spam bounces that are very, very
similar to some of the domain errors shown above. The
first is a Domain Not Found error, where the sender's
domain could not be found:
<recipient@pobox.com>:host cali-1.pobox.com said: 554
<user@fake_domain.com>: Sender Address Rejected: domain not found
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Unlike the Domain Not Found error shown above as a domain
error, this is an anti-spam bounce. Notice the
"Sender Address Rejected"; this means that
the problem is actually with the Sender's email address -
specifically, that the domain used in the sender's email
address was not a valid domain. When a mail server receives
an email for one of its users, the server checks to ensure
that the sender's domain is a real domain - if the domain
name does not resolve, the message is rejected with the
"Sender Address Rejected" error. This is an
anti-spam error in that it prevents mail servers from
accepting spam where the domain is completely fake, meaning
the message could not really have originated there.
The other type of "554 Relay Access Denied"
error is a problem with the sender using the wrong
mail server to send their message:
<sender@pobox.com> host smtp-gw-4.msn.com said:
554 <sender@pobox.com>: Sender Address rejected:
Relay access denied
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Essentially, this error message is similar to a
Recipient Address rejected, in that the server
reporting the error does not like the domain name; however,
in this case, the problem is that the outgoing email server
did not like the domain of the sender's email address (as
opposed to the above Recipient errors, where the incoming
mail server does not like the recipient's domain).
What this error generally indicates is that the outgoing
server you're using (usually the one assigned to you by your
ISP) will not accept email with the From: address you've
used on the email. For example, domains such as
BellAtlantic.com, GTE.net, and Verizon.com do not allow
users to send email their outgoing mail server if the
"From" email address used on the message is not
the one assigned by them (e.g. you can't send out mail
that uses your Pobox address as the From: header via their
mail servers).
Many ISPs have begun to enforce these restrictions to
prevent spammers from using the ISP's access and SMTP server
to send spam. To remedy this error,
you will need to use the email address assigned to you by
the provider as the From: address on outgoing email.
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