Don't restart Dovecot first. Read first.
1. What's the user-visible symptom? "Can't log in", "messages disappeared", "slow"?
2. Check service status:
systemctl status dovecot
doveconf -n | head -50
3. Tail the right log with the user's pid:
tail -F /var/log/dovecot.log /var/log/dovecot-info.log | grep alice@example.com
4. Replay the failing operation while watching the log. Most issues print a clear error within 5 seconds.
5. Inspect mailbox state:
doveadm mailbox status -u alice@example.com all INBOX
doveadm fetch -u alice@example.com 'uid hdr.subject' mailbox INBOX last 5
doveadm is your Swiss Army knife — read its man page once and refer back forever.
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