After entering a wrong IMAP password, the login is irresponsive, nothing happens

Dovecot tracks login failures and delays logins after a login failed. This is a feature called Authentication Penalty. You can check the current penalties with

doveadm penalty

IMAP login fails with Thunderbird when password contains non ASCII characters

The IMAP protocol originally only allowed ASCII characters to be used for passwords. Most servers and clients support UTF-8 by now. Thunderbird 1 still transmits the password in ASCII. Because of this the hash Dovecot makes differs from the UTF-8 version of the password and Dovecot rejects the password, yielding a "Password mismatch" error.

Possible solutions are:

  • use a different mail client
  • only use ASCII characters in passwords

You are receiving e-mails with the subject "Report Domain: Submitter:...."

These e-mails are send by other e-mail servers that receive e-mails claiming to come from (your domain). If either SPF or DKIM fails, these e-mails are rejected and the e-mail you specifed using the rua= record in the DMARC record. If you are receiving these e-mails after following this tutorial or after changes you made, it is likely that your DKIM or SPF configuration is faulty. Or someone is trying to spoof e-mails using your domains. Check the attached report for more details. You can see whether DKIM or SPF failed and what IP was sending the e-mail.

  1. Observed with Thunderbird 52.8.0.