I also encountered this issue when upgrading Kubuntu, from 24.04 to 26.04.1.
$ sudo ls -hal /etc/postfix total 60K drwxr-xr-x 4 root root 4.0K Sep 12 20:35 . drwxr-xr-x 177 root root 12K Sep 12 20:31 .. -rw-r--r-- 1 root root 60 Nov 29 2021 dynamicmaps.cf -rw-r--r-- 1 root root 2.4K May 5 23:45 main.cf.proto lrwxrwxrwx 1 root root 31 Nov 29 2021 makedefs.out -> /usr/share/postfix/makedefs.out -rw-r--r-- 1 root root 6.2K Nov 29 2021 master.cf -rw-r--r-- 1 root root 7.2K May 5 23:45 master.cf.proto -rw-r--r-- 1 root root 9.1K May 5 23:45 postfix-files drwxr-xr-x 2 root root 4.0K May 5 23:45 postfix-files.d drwxr-xr-x 2 root root 4.0K May 5 23:45 sasl -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2165958 Title: package postfix 3.10.6-4ubuntu2.1 failed to install/upgrade: old postfix package postinst maintainer script subprocess failed with exit status 1 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/postfix/+bug/2165958/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
