SMTP Fixup Issue

From Roaring Penguin
Revision as of 12:23, 15 March 2016 by MCoyne (talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

This may also be referred to as SMTP Inspection and is a feature on Cisco firewalls. Unfortunately it causes what are often hard to diagnose intermittent blocking of email passing through the firewall and is considered a useless anti-spam feature by most. The following article contains more detail:

To determine if this feature is in the mail delivery path for your mail server go to an external computer and open a terminal window. Then telnet to your mail server on port 25 as shown below:

root@colo4(~)# telnet 25
Connected to
Escape character is '^]'.
220 *************************************************************************************************

The long line of "*" is the indicator of the feature being in place. We strongly recommend that the feature be disabled on the firewall.