Date: Wed, 3 Jan 2007 15:55:52 -0800 From: "Derrick Ryalls" <ryallsd@gmail.com> To: FreeBSD-questions <questions@freebsd.org> Subject: Is there a solution for 550 User Unknown mails Message-ID: <d5eb95fc0701031555q1146a593tbb1c9a7de08b2626@mail.gmail.com>
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This is perhaps off topic, but all machines in question are running FreeBSD :)
Every day I get dozens of failed email notifications in the form of:
UNDELIVERABLE MAIL Your message to the following recipients cannot be
delivered: <wtcxqomfaq@alicedsl.de>: webmail.hansenet.de
[213.191.73.2]:
RCPT TO:<wtcxqomfaq@alicedsl.de>
<<< 550 RCPT TO:<wtcxqomfaq@alicedsl.de> User unknown
This user Unknown message is due to my server rejecting a mail to my
domain (my domain is not alicedsl.de) for an Unknown user. Doing some
reading, it appears that in a perfect system where there is only 1
email server per domain, I won't recieve these messages since during
the whole email conversation I will tell the person talking to me that
I don't know of that account and no extra email is generated.
With secondary mail servers, I am accepting mail for other domains,
and then forwarding them on. It is my belief that acting as a
secondary mail server is what is causing me to receive all these
errors. What I believe is happening is that for whatever reason the
spammer is talking to my email server for a domain I am secondary on.
I accept the mail and finish the conversation. I then talk to the
main email host to let them know of the email I got for them. The
master host responds with 550 User Unknown as it should. Being the
good little secondary email server I am, I try to respond to the
sender that they got the wrong address, which turns out to be fake.
Assuming that my guessing is correct, is there any way to stop this
flood of reject emails short of not being a secondary server for
anyone?
If my guesses are incorrect, then what is actually going on and how do
I stop the flow?
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