SMTP data timeout (message abandoned) on connection from...

Problems/questiong regarding daily usage of MailCleaner

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opg1987
Posts: 44
Joined: Thu Dec 17, 2015 12:14 pm
How did you hear about Mailcleaner: Colleague

SMTP data timeout (message abandoned) on connection from...

Postby opg1987 » Wed Nov 29, 2017 10:34 am

Hi all,

I have an issue with some emails with attachments not getting through.

I have an SMTP proxy on my firewall that performs spam blocking and AV scanning. This then forwards to our MailCleaner server (which runs as a secondary spam filter and primarily a quarantine server).

Some emails from certain addresses containing attachments seem to not get through. When checking the 'Incoming MTA' log on our mailcleaner, I can see entries for these addresses showing:

SMTP data timeout (message abandoned) on connection from mail.domain.com [123.123.123.123] F=<john.smith@domain.com>

When I turn off the SMTP proxy on our fire wall and revert to a straight NAT run from external IP to Mailcleaner IP, this no longer happens and the emails that were receiving this message in the log come through (presumably once the sending mail server retries delivery).

Any ideas what might be causing this? Most of the settings on the SMTP proxy are default, we simply AV scan all attachments and SPAM check.

I thought it might be our 'SMTP session timeout' setting but this has been increased to 20 minutes (primarily for testing this theory) with no luck.

Has anyone dealt with this issue before? Any suggestions with where else to look?

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