[Exim] "SMTP protocol violation: synchronization" error when…

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Author: Ralf Hauser
Date:  
To: exim-users
Old-Topics: Re: [Exim] Intermittently connected host is a Windows 2000 server with dynamic IP
Subject: [Exim] "SMTP protocol violation: synchronization" error when using TLS with Outlook on a port other than 25?
We are trying to receive mail from various MUAs with exim protected by TLS.

Works fine with Mozilla Messenger, K-Mail etc.
When doing the same with Outlook, we got
<<...
SMTP protocol violation: synchronization error (next input sent too soon):
rejected "<80>j^A^C^A" H=[10.2.1.1]
5217 SMTP>> 554 SMTP synchronization error
...>> and it dies.
In Outlook, one sees for example:
<<The TCP/IP connection was unexpectedly terminated by the server.>>

Using tcpflow to compare what is going "over the wire", we noticed that
Outlook isn't sending
<<EHLO my.computer.com
STARTTLS
idhflkjasdhfasdhfoosahdflksdhf
...>> like the other MUAs do, but appears to directly send SSL'ed
information.

ssh tunneling via localhost's port 25 to the true server's port (other than
25) is a work-around for testing provided one has ssh access to the mail
host.
So, outlook seems to behave differently depending on whether it is going for
port 25 or other ports.

Therefore my question: has anybody been successful at running a production
exim with SMTP-TLS on a port other than 25 with Outlook users?