You are having problems sending/receiving E-Mails and wonder why:

Q1) Where are the log files?

su; # become admin
doveadm log find; # find the location of the log files

Debug: /var/log/dovecot.log
Info: /var/log/dovecot.log
Warning: /var/log/dovecot.log
Error: /var/log/dovecot.log
Fatal: /var/log/dovecot.log

less +F /var/log/dovecot.log; # open the file with less in FOLLOW mode, meaning: it will update LIVE as soon as new lines are generated by dovecot
# you can cancel FOLLOW mode by hitting Ctrl+C, now you can scroll up and down with the arrow keys through the log file
# same navigation as with vim, hit g twice [g][g] (g twice) to get to beginning of file, hit [G][G] (Shift+G twice) to go to end of file

if you now send an E-Mail dovecot should generate some line like:

Apr 27 14:12:55 imap-login: Info: Login: user=, method=PLAIN, rip=, lip=, mpid=32107, TLS, session=<8G59qrMU6gAFx7De>
# mpid = master process id, rip = ? , lip = ?