- Plesk Onyx for Linux
- Microsoft Outlook 365 application fails to connect email server via IMAP.
- No account email displayed in Inbox.
- Courier-IMAP mail server is used.
/var/log/maillogfile contains the following entries:
CONFIG_TEXT: ns2 courier-imaps: LOGIN, firstname.lastname@example.org ip=[203.0.113.2], port=, protocol=IMAP
srv courier-imaps: Unexpected SSL connection shutdown.
SSL protocol negotiation fails by unknown reason
1. Log into Plesk
2. Switch IMAP server service from "Courier-IMAP" to "Dovecot"
Navigate to Home > Tools & Settings > Updates and Upgrades > Mail hosting > IMAP/POP3 servers and set Mail server to Dovecot.