Debugging tries to log as much as possible. There are a few places where you can find valuable logs for debugging:

  1. docker logs --tail=100 mailserver
    there should be all the information about starting and stopping services.
  2. /your-data-dir/logs
    its essentially a copy of /var/log from the inner container. There are a few special directories in addition to the standard ones:
    • admin-app - web administration errors log
    • delivery - all email delivery logs should be logged there
    • dmarc - received DMARC reports
    • s6 - contains output from supervised services
  3. /your-data-dir/domains/
    whenever the sieve script fails, the error should be logged in this file in the user's mailbox directory

PRO version

PRO version allows you to browse delivery logs via web administration.