Issue postfix still using ipv6 even if Outgoing mail mode is configured to use IPv4 alone

[nisamudeen97]

Server operating system version

CentOS Linux release 7.9.2009

Plesk version and microupdate number

Version 18.0.54 Update #4, last updated on Aug 29, 2023 10:09 AM

Hi,

We have started getting email bounce back by saying IPV6 not having RDNS. When checked we could see postfix still using ipv6 even if Outgoing mail mode is configured to use IPv4 alone. See the current screen shot setting, Mail server is configured to use IPV4 alone. But out going emails are found using IPV6.



When checked /etc/postfix/main.cf, inet_protocols I could see that it was configured to use All. I have changed the value manually to
inet_protocols = ipv4 and restarted postfix. Now emails are going via IPV4.

I could recollect that I have done the same thing before and plesk update has reverted the setting back to All. So in this case two issues are there.


1. How can I make sure plesk uses IPv4 alone to send outgoing emails? Why the setting change from front end is not changing on back end. ?
2. How to avoid main.cf custom settings getting reverted

 

[Peter Debik]

The outgoing mail mode does not limit Postfix to IPv4 or IPv6, it only defines from which IP addresses mails are being sent. It is possible to allow Postfix to mail with both inet_protocols, yet to send only from IPv4 when emails are sent. However, with the inet_protocols variable you can tell Postfix how Postfix shall transmit mails to another MTA. This setting is persistent and of no interest to Plesk, like many other settings in the main.cf file that are not touched by Plesk. Even if you set "IPv4" to "none" and "IPv6" to an IP address offered in the drop down, the "inet_protocols" line will remain unchanged.

So if your inet_protocols setting was changed, it must be for a different reason.

 

[nisamudeen97]

Hi,

Thank you very much for your update. I think my recent plesk update has caused this. What about below KB topic? Is it related to my issue?

Why customization of /etc/postfix/main.cf and /etc/postfix/master.cf on a Plesk server gets reverted? - Support Cases from Plesk Knowledge Base

Why customization of /etc/postfix/main.cf and /etc/postfix/master.cf on a Plesk server gets reverted? - Support Cases - Plesk Knowledge Base

www.plesk.com

 

[Peter Debik]

That would be new to me that on a Postfix upgrade, the main.cf file is reverted to a default version. I've never had that during the past eight years with Plesk. On a "plesk repair mail" though, yes, that is a different case.

 

[nisamudeen97]

The same issue has started again. When checked i could see main.cf is reset and postfix started using IPV6 again.

[root@fpostfix]# ls -lt |grep main.cf

-rw-r--r-- 1 root root 29966 Oct 14 03:22 main.cf

Postfix was updated in Oct 4

Oct 04 10:17:36 Updated: 2ostfix-3.5.14-2.centos.7+p18.0.48.0+t220930.1630.x86_64