Thunderbird or Outlook Won’t Save Sent Messages (imap/dovecot)

You’re getting an error that Outlook or Thunderbird cannot save to the sent folder and you’re connected to an imap server running dovecot. You’re also seeing Maximum Number of User+IP connections in /var/log/maillog as people try to send email messages.

Please edit the following configuration to accept more simultaneous connections from a single IP. Add it if missing.

/etc/dovecot/dovecot.conf

Add or edit the line and increase it.

mail_max_userip_connections = 50

Restart dovecot via

systemctl restart dovecot