Poste.io try to log as much as possible. There are couple places where you can find valuable logs when debugging:
docker logs --tail=100 mailserverthere should be all information about starting and stopping services.
/your-data-dir/logsits essentially copy of /var/log from inner container. There are couple special directories besides standard ones:
- admin-app - web administration errors log
- delivery - all logs from email delivery should be logged there
- dmarc - received DMARC reports
- s6 - contains output from supervised services
/your-data-dir/domains/domain.com/username/.dovecot.sieve.logwhenever sieve script fails there should be error logged to this file under user mailbox directory
In PRO version you can search through delivery logs at web administration.