Outlook mail client fails to connect to the Plesk server: "We couldn't connect to the incoming (IMAP) server using the specified encryption method"

Symptoms

• Outlook mail client fails to connect to the Plesk server over IMAP SSL port 993 with the error message:

  PLESK_INFO: We couldn't connect to the incoming (IMAP) server using the specified
  encryption method. Please check the incoming (IMAP) server
  encryption method and try again.

  ---

  PLESK_INFO: None of the authentication methods are supported by Outlook are supported by your server.

• The following error message is logged in /var/log/maillog:

  CONFIG_TEXT: warning: TLS library problem: error:0A000102:SSL routines::unsupported protocol:ssl/statem/statem_srvr.c:1657

Cause

The ssl_min_protocol value in Dovecot configuration is set to TLSv1.3 which is not supported by Outlook mail client.

Resolution

1. Connect to the Plesk server via SSH.

2. Enable TLSv1.2 protocol in Dovecot configuration: 

   # plesk sbin sslmng --services dovecot --protocols 'TLSv1.2'

3. Restart the Dovecot service:

   # service dovecot restart