Symptoms

1. When trying to set up an IMAP account in Outlook or Samsung Email android app, IMAP option is not available in the “Account type” field
2. One of the following errors can be found in /var/log/maillog on Plesk server:

   server dovecot: imap-login: Disconnected: Inactivity during authentication (client didn’t finish SASL auth, waited 179 secs): user=<>, method=DIGEST-MD5, rip=127.0.0.1, lip=127.0.0.1, TLS, session=<Uzcj+sRVW+J/AAAB></>

   imap-login: Disconnected (auth failed… The issue is not reproduced in other mail clients, like Thunderbird.

   SASL DIGEST-MD5 authentication failed: authentication failure

Cause

Current implementation of a DIGEST-MD5 authentication in libsasl2-2 package is incompatible with Microsoft Outlook. Additional details can be found here.

Resolution

Note: if you don’t have root access to Plesk server via SSH, contact your hosting provider regarding the issue

1. Login to Plesk server over SSH
2. Create a custom configuration file and place the auth_mechanisms parameter without digest-md5:

   # vi /etc/dovecot/conf.d/00-auth_mechs.conf

   auth_mechanisms = plain login cram-md5 apop

3. Restart Dovecot to apply the configuration changes:

   # service dovecot restart