[Koha] Where are SMTP errors logged?

[Chris Brown]

I defined an SMTP server for one of my koha libraries, but it is failing to
send messages. Another library (on the same server) is working OK with the
same SMTP server settings, as far as I can see. I have set the Debug mode
to "enabled" on the SMTP server settings. Can you tell me where the
debug output goes? We are using koha 22.11

Thanks!

Chris Brown