Public bug reported: With Bionic, Sendmail would send email over IPv4 and IPv6, which I could see in logs and DMARC aggregate reports. Since upgrading to Focal, it's only attempting to send over IPv4, but I can receive email just fine over IPv4 or IPv6. I'm seeing that both with an upgrade and a fresh install.
On further testing, it looks like Sendmail in 20.04 isn't even trying to get IPv6 addresses for servers. If only an IPv6 address is available, I get a "host unknown" bounce. What changed, then? Not my configuration, in the case of the upgrade, and I don't see anything relevant in the package changelogs between the 2 versions. ** Affects: ubuntu Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1894379 Title: No IPv6 outbound from Sendmail starting with 20.04 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+bug/1894379/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs