From: Mark Martinec (Mark.Martinec+postfixijs.si)
Date: Fri Dec 01 2006 - 09:34:20 CST

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Hrvoje,

> I found that on one of my servers, queue is full of messages with 550
> reject error. At first, i was puzzled why would message with 550 error end
> up i queue, instead of rejected. After a short time, i found out that
> destination server is sending quite strange 550 error message:
>
> # telnet 65.24.7.64 25
> Trying 65.24.7.64...
> Connected to 65.24.7.64.
> Escape character is '^]'.
> 550-clmboh-mx-10.mgw.rr.com
> 550 ERROR: Mail Refused - x.x.x.x - See http://securit...
>
> I did read through rfc, and i think this isn't correct response code to
> connect, but i would like to others verify this.

It is almost correct - a 'by the book' greeting response should have been 554.

rfc2821:

3.1 Session Initiation
[...]
   The SMTP protocol allows a server to formally reject a transaction
   while still allowing the initial connection as follows: a 554
   response MAY be given in the initial connection opening message
   instead of the 220. A server taking this approach MUST still wait
   for the client to send a QUIT (see section 4.1.1.10) before closing
   the connection and SHOULD respond to any intervening commands with
   "503 bad sequence of commands". Since an attempt to make an SMTP
   connection to such a system is probably in error, a server returning
   a 554 response on connection opening SHOULD provide enough
   information in the reply text to facilitate debugging of the sending
   system.

Mark

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