Issue After updates last night all my servers are getting returned mail

[Azzitude]

Server operating system version

Rocky Linux 8.7 and CentOs 7.9

Plesk version and microupdate number

18.0.48

Auto updates 12 December 2022 have broken something as all of my servers are now doing this

Undelivered Mail Returned to Sender

these are Plesk server notifications, not domains sending emails

 

[Peter Debik]

Have you checked your /var/log/maillog what the course of these mails is? Maybe you can find out more about it there.