Outgoing mail suddenly stops working

Virtualmin
1

Hello,

With the help of @calport I have been able to successfully send/receive mail on my server for about a month now but I suddenly noticed that outgoing mail stopped working all of a sudden (Mail was reported as being sent successfully regardless of sending via roundcube, usermin or the virtualmin dashboard but it never ended up going anywhere).

I tried sending a test email to mail-tester but they didn’t received the email. The mail log files shows the following:

Sep 28 01:55:55 mbox postfix/qmgr[8194]: 7A341102B4E: from=<abc@example.com>, size=38601, nrcpt=1 (queue active)
Sep 28 01:55:56 mbox postfix/smtp[11611]: warning: srv1.mail-tester.com: dane configured with dnssec lookups disabled
Sep 28 01:56:26 mbox postfix/smtp[11611]: connect to reception.mail-tester.com[94.23.206.89]:25: Connection timed out
Sep 28 01:56:26 mbox postfix/smtp[11611]: 7A341102B4E: to=<test-eo6vd2rye@srv1.mail-tester.com>, relay=none, delay=4646, delays=4615/0.03/30/0, dsn=4.4.1, status=deferred (connect to reception.mail-tester.com[94.23.206.89]:25: Connection timed out)
Sep 28 02:00:55 mbox postfix/qmgr[8194]: AEBBB102B6C: from=<abc@example.com>, size=770, nrcpt=1 (queue active)
Sep 28 02:00:55 mbox postfix/smtp[12317]: warning: srv1.mail-tester.com: dane configured with dnssec lookups disabled
Sep 28 02:01:25 mbox postfix/smtp[12317]: connect to reception.mail-tester.com[94.23.206.89]:25: Connection timed out
Sep 28 02:01:25 mbox postfix/smtp[12317]: AEBBB102B6C: to=<test-6rhgvfv5a@srv1.mail-tester.com>, relay=none, delay=4750, delays=4719/0.03/30/0, dsn=4.4.1, status=deferred (connect to reception.mail-tester.com[94.23.206.89]:25: Connection timed out)
Sep 28 02:04:14 mbox postfix/smtpd[12937]: connect from unknown[193.169.254.106]
Sep 28 02:04:16 mbox postfix/smtpd[12937]: warning: unknown[193.169.254.106]: SASL LOGIN authentication failed: authentication failure
Sep 28 02:04:17 mbox postfix/smtpd[12937]: lost connection after AUTH from unknown[193.169.254.106]
Sep 28 02:04:17 mbox postfix/smtpd[12937]: disconnect from unknown[193.169.254.106] ehlo=1 auth=0/1 commands=1/2
Sep 28 02:06:30 mbox dovecot: imap-login: Login: user=<abc@example.com>, method=PLAIN, rip=2401:4900:3a7b:1cc0:83e3:70ab:a158:427c, lip=2602:fe90:300:1a2::6f10:5c2d, mpid=12992, TLS, session=<FpRhHVawnLIkAUkAOnscwIPjcKuhWEJ8>
Sep 28 02:06:31 mbox dovecot: imap(abc@example.com): Connection closed (LIST finished 0.389 secs ago) in=50 out=1076
Sep 28 02:06:34 mbox dovecot: imap-login: Login: user=<abc@example.com>, method=PLAIN, rip=2401:4900:3a7b:1cc0:83e3:70ab:a158:427c, lip=2602:fe90:300:1a2::6f10:5c2d, mpid=12994, TLS, session=<YlKcHVawnrIkAUkAOnscwIPjcKuhWEJ8>
Sep 28 02:06:35 mbox dovecot: imap(abc@example.com): Connection closed (UID SEARCH finished 0.288 secs ago) in=81 out=1223
Sep 28 02:06:38 mbox dovecot: imap-login: Login: user=<abc@example.com>, method=PLAIN, rip=2401:4900:3a7b:1cc0:83e3:70ab:a158:427c, lip=2602:fe90:300:1a2::6f10:5c2d, mpid=12996, TLS, session=<OQHZHVawoLIkAUkAOnscwIPjcKuhWEJ8>
Sep 28 02:06:40 mbox dovecot: imap(abc@example.com): Connection closed (UID FETCH finished 0.306 secs ago) in=151 out=1449
Sep 28 02:07:37 mbox postfix/anvil[12939]: statistics: max connection rate 1/60s for (smtp:193.169.254.106) at Sep 28 02:04:14
Sep 28 02:07:37 mbox postfix/anvil[12939]: statistics: max connection count 1 for (smtp:193.169.254.106) at Sep 28 02:04:14
Sep 28 02:07:37 mbox postfix/anvil[12939]: statistics: max cache size 1 at Sep 28 02:04:14
Sep 28 02:10:55 mbox postfix/qmgr[8194]: E730B102489: from=<abc@example.com>, size=3364, nrcpt=1 (queue active)
Sep 28 02:10:55 mbox postfix/smtp[13771]: warning: yahoo.in: dane configured with dnssec lookups disabled
Sep 28 02:11:25 mbox postfix/smtp[13771]: connect to mx-apac.mail.gm0.yahoodns.net[106.10.248.74]:25: Connection timed out
Sep 28 02:11:55 mbox postfix/smtp[13771]: connect to mx-apac.mail.gm0.yahoodns.net[106.10.248.73]:25: Connection timed out
Sep 28 02:11:56 mbox postfix/smtp[13771]: E730B102489: to=<xyz@ymail.com>, relay=none, delay=23739, delays=23679/0.03/60/0, dsn=4.4.1, status=deferred (connect to mx-apac.mail.gm0.yahoodns.net[106.10.248.73]:25: Connection timed out)

When I run re-check configuration in Virtualmin, everything returns fine.

What could be causing this issue?

2

connections time out, you cant reach smtp… maybe check your firewall for blocks…

3

@dimitrist What would be the right way to go about checking firewall blocks? I tried to telnet port 25 of the server and it seems to be open.

4

your outgoing connections FROM your server fail. so check from inside your server like:
$ telnet reception.mail-tester.com 25
or if you use nmap :
$ nmap -p25 reception.mail-tester.com

if you get connections timeout, check your server firewall’s outgoing settings.

5

So it turns out that it was the ISP who was blocking the SMTP connections (not sure why though since I asked them if it was because of a spam issue and they said no) and have now unblocked it again.

Thanks for the help @dimitrist

6

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