I am having an issue with an ASA 5510, running 8.4(1) code, causing outbound mail to remain in the SMTP server queue (Exchange 2007). This only happens with some remote mail servers. The connection usually ends with the remote server eventually sending a TCP reset.
I've taken multiple inside and outside packet traces...
One trace shows the following at the end of the TCP stream:
X
421 4.4.2 service timed out.
QUIT
Other trace's contain either X's preceding various sections of the stream content or all X's in the content. The X's only appear when inspection is enabled.
Disabling inspection is the only thing that seems to allow mail to flow. I find this curious because I'm running this same ESMTP policy on other ASA's. However, they are on 8.3 code.
Has anyone experienced this or have an idea how to fix the issue? Most everything I find when searching on this subject says to disable ESMTP inspection. However, that isn't a good permanent solution.
Current Custom ESMTP Policy:
policy-map type inspect esmtp esmtp_tls_enable
description Custom ESMTP policy-map w/ TLS enabled
parameters
no mask-banner
allow-tls action log
match cmd line length gt 512
log
match cmd RCPT count gt 100
log
match body line length gt 998
log
match header line length gt 998
log
match MIME filename length gt 255
log
match sender-address length gt 320
log
match ehlo-reply-parameter others
mask
