Re: IPv6 recap
Joe Laffey <[email protected]>
| Newsgroups | gmane.mail.imap.courier.general |
|---|---|
| Message-ID | <[email protected]> |
On Fri, 5 Apr 2024, Alessandro Vesely wrote: > On Fri 05/Apr/2024 14:08:27 +0200 Sam Varshavchik wrote: >> Alessandro Vesely writes: >> >>> this happened again, but this time caused a bounce: >>> >>> <<< 554 resimta-c2p-559421.sys.comcast.net >>> resimta-c2p-559421.sys.comcast.net 2a02:29e1:500:6c00::4 Comcast requires >>> that all mail servers must have a PTR record with a valid Reverse DNS > entry. >>> Currently your mail server does not fill that requirement. For more >>> information, refer to: > https://postmaster.comcast.net/smtp-error-codes.php#554 >>> >>> Is it possible to inhibit use of IPv6 a little bit harder? >> >> Can you block all IPv6 connections to port 25 on your firewall? I ran into this same issue. There does not seem to be a way to disable IPv6 in Courier (without possibly recompiling). No matter what, courier tries to send out via IPV6. I even disabled IPv6 in sysctl, and in the boot loader options under Linux. After I disabled IPV6 it still didn't work. Courier tries to bind to a non-existent IPv6 address (none is assigned at all, IPv6 disabled, and no IPv6 shows up in 'ip a' output). It gives these errors in the log: 'Cannot assign requested address' and mail to IPv6 relays gets stuck in the queue. This is even after setting the system resolver to prefer ipv4. I suppose if I was using a resolver where I could configure it to NEVER return ipv6 MX entries that would work. Eventually I just set up proper forward and reverse DNS entries for IPv6 and all works fine. Note other mail servers have the ability to disable ipv6 in the config. Postifx actually does it automatically (and tells you about it over and over). Would be nice if courier had an option to completely disable IPv6, or at least didn't try to bind to a non-existent IPv6 address. Hopefully I am wrong about the above and this was user error, but those are my findings. -- 73 Joe Laffey _______________________________________________ courier-users mailing list [email protected] Unsubscribe: https://lists.sourceforge.net/lists/listinfo/courier-users