From: Mezei Zoltán (mezei.zoltantelefor.hu)
Date: Thu Jan 12 2006 - 05:44:07 CST

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Hi,

I've just finished setting up a new postfix mail server.

However when receiving mail from some mail servers, they just wasn't
delivered. I finally solved the problem, and here is the description, it
may be useful.

The SMTP chat begun correctly, EHLO, MAIL FROM and RCPT TO was sent and
answered. After that postfix received DATA and answered

"354 End data with <CR><LF>.<CR><LF>"

No answers came after that, and the TCP package was repeated many times,
before the 5 mins timeout exceeded. After that the DATA transfer ended
without success.

The postfix logs didn't say any other useful info, neither did
tcpdump/tethereal.

I looked at the documentation and found in the faq that it should be a
cisco pix problem or an MTU problem - neither solution mentioned there
helped.

After hours of trying I found out that changing the 354 message to:

"354 Start mail input; end with <CRLF>.<CRLF>"

solves the problem. This is the exact recommendation from the RFC. I
_know_ that it is a recommendation and it doesn't mean that you have to
use the exact same string.

I tried to contact the sysadmin of the other side. The domain belonged
to a Hungarian bank, so he wasn't allowed to provide information about
their system (proxies, mail servers) but assured me that I was right:
they check for the exact same string that appears in the second quote.

Is it maybe possible to implement a feature in postfix to allow
changeable 354 (and other SMTP) messages? I know the problem isn't in
postfix but in the other mail system, but this change won't ruin
anything and would help some people. I lack the C programming knowledge
to implement this feature.

Thanks for reading,

Zizi

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