On Sat, Jun 06, 2026 at 16:47:53 +0200, Kamil Jońca wrote: > Michel Verdier <[email protected]> writes: > > > On 2026-06-06, Kamil Jońca wrote: > > > >> both "mail.kjonca" and "news.kjonca" are cnames for host with address > >> 192.168.200.200 - local host interface (!=localhost) > > > > It is not related to your problem but some services do not like names not > > ending with a correct tld. So you should use something like > > mail.kjonca.net instead of mail.kjonca. > Again: why this worked with older kernels?
I keep thinking it's probably something in the networking code. I'm reminded of TCP Window Scaling, which caused a bunch of problems when it was newly introduced. Devices which were not properly configured sometimes could not communicate properly with Linux systems that had TCP Window Scaling enabled. (This was not a bug in Linux. It was a common bug or misconfiguration in other systems.) What kind of device is 192.168.200.200? Is it running Linux, or something else?
