Resolved Postfix unable to send some mails: deferred

[Nicola Urbinati]

Hi,

We're having a problem with postfix (Ubuntu 18.04.04, Obsidian 18.0.21 update #1), unable to send some mails, that remain deferred for days.

Here's some lines from mail.log:

postfix/smtp[18169]: 0AAB71240D32: to=<[email protected]>, relay=none, delay=8873, delays=8867/0.03/6.5/0, dsn=4.4.1, status=deferred (connect to mx-eu.mail.am0.yahoodns.net[188.125.72.74]:25: Connection refused)
postfix/smtp[25102]: C38BC1241292: to=<[email protected]>, relay=none, delay=2298, delays=2293/0.02/5.1/0, dsn=4.4.1, status=deferred (connect to alt4.gmail-smtp-in.l.google.com[173.194.202.27]:25: Connection refused)

Here's what seems a full transition:
postfix/smtp[5461]: E5971124104F: to=<[email protected]>, relay=127.0.0.1[127.0.0.1]:10024, conn_use=2, delay=265, delays=0.01/186/0/79, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp:[127.0.0.1]:10025): 250 2.0.0 Ok: queued as BDA281240FDC)
postfix/smtp[6209]: BDA281240FDC: to=<[email protected]>, relay=none, delay=5.2, delays=0.01/0/5.2/0, dsn=4.4.1, status=deferred (connect to alt4.gmail-smtp-in.l.google.com[173.194.202.26]:25: Connection refused)

If I "telnet alt4.gmail-smtp-in.l.google.com 25", I get the following response, getting the proper connection:
Connected to alt4.gmail-smtp-in.l.google.com.
Escape character is '^]'.
220 mx.google.com ESMTP j19si166558pga.271 - gsmtp

What's going on?

 

[Nicola Urbinati]

Here is a full log for an outgoing mail (not all mails get stucked like this):

Nov 20 09:32:16 srvurb01 postfix/smtp[26537]: B8A9F124135D: to=<[email protected]>, relay=127.0.0.1[127.0.0.1]:10024, delay=96, delays=0.33/0.01/0.01/96, dsn=2.0.0, status=sent (250 2.0.0 from MTA(smtp:[127.0.0.1]:10025): 250 2.0.0 Ok: queued as 09CE71241360)
Nov 20 09:32:16 srvurb01 postfix/qmgr[5502]: B8A9F124135D: removed
Nov 20 09:32:17 srvurb01 postfix/smtp[26772]: connect to gmail-smtp-in.l.google.com[66.102.1.26]:25: Connection refused
Nov 20 09:32:18 srvurb01 postfix/smtp[26772]: connect to alt1.gmail-smtp-in.l.google.com[209.85.233.26]:25: Connection refused
Nov 20 09:32:19 srvurb01 postfix/smtp[26772]: connect to alt2.gmail-smtp-in.l.google.com[142.250.4.26]:25: Connection refused
Nov 20 09:32:20 srvurb01 postfix/smtp[26772]: connect to alt3.gmail-smtp-in.l.google.com[108.177.97.27]:25: Connection refused
Nov 20 09:32:21 srvurb01 postfix/smtp[26772]: connect to alt4.gmail-smtp-in.l.google.com[173.194.202.26]:25: Connection refused
Nov 20 09:32:21 srvurb01 postfix/smtp[26772]: 09CE71241360: to=<[email protected]>, relay=none, delay=5.2, delays=0.02/0.01/5.1/0, dsn=4.4.1, status=deferred (connect to alt4.gmail-smtp-in.l.google.com[173.194.202.26]:25: Connection refused)

 

[Nicola Urbinati]

Ok,

Found out the problem: ConfigServer set with SMTP_BLOCK = On.

With that option set to OFF, all traffic is now going fine.

 

[Nicolas Stephanou]

Hi Nicola
I'm having a similar issue, but I'm not sure where to find ConfigServer.
Thanks

 

[Nicola Urbinati]

Hi Nicolas,

ConfigServer is CSF, a popular Firewall and Intrusion Detection software you can add to Plesk, manually or trhough some extensions (Juggernaut for example).

So you could have it enabled by one of such extensions, or you could have another similar software doing it (blocking outgoing SMTP connections).

Also check port 25 (or your SMTP port if different).