On Mon, Oct 17, 2022 at 05:37:47PM +0200, Gerald Galster wrote: > >> This is very strange and I can confirm it. > > > > Can you test the other (working) certificate again? In Outlook set the > > hostname as per certificate and in local hosts file in Windows force > > IP of the destination server for this hostname. This way Outlook > > should not complain about mismatched hostnames... > > > Unfortunately I can't experiment with certificates (customer says > this has been enough trouble). > > Can you check the certificates' serial numbers? > The working one begins with 03 and the problematic one with 04. > > There are 37 archived certificates for this hostname, 29 begin > with "03" and only 8 with "04". > > Certificates starting with "04" occur since autumn 2019. > After that date it's sometimes "03" and sometimes "04".
This looks exceedingly unlikely to be relevant. -- Viktor.