exim configuration: 503 AUTH command used when not advertised

Posted by jrdioko on Server Fault See other posts from Server Fault or by jrdioko
Published on 2011-09-20T18:24:04Z Indexed on 2012/04/07 11:34 UTC
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I'm running a piece of software on a Windows server that sends email notifications via a remote SMTP server. It has very few configuration options, and only supports basic SMTP authentication without SSL/TLS. I have exim4 running on a Debian server that will be the SMTP server for this Windows program. It is set up with default configuration, plus allowing AUTH PLAIN and AUTH LOGIN unencrypted connections. I have successfully sent an email over telnet:

telnet servername 25
ehlo test
250-AUTH PLAIN LOGIN
...
auth plain XXX
235 Authentication succeeded
mail from: ...
...

However, the program I want to connect to this server fails to connect. To see why, I ran a packet sniffer during the connection, and see the following session:

C: HELO hostname
S: 250 Hello hostname
C: AUTH LOGIN XXX | XXX
S: 503 AUTH command used when not advertised | 500 unrecognized command
C: QUIT
S: 221 closing connection

I'm not familiar enough with the SMTP protocol to understand what's going on here. What do I need to change on my exim4 SMTP server to allow for this connection to be made?

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