- On a Plesk for Linux server, Postfix is used as a mail server.
- SMTPS connection from Outlook to the Plesk server fails to be established.
- The following errors are found in the file
CONFIG_TEXT: SSL_accept error from unknown[203.0.113.2]: lost connection
lost connection after CONNECT from unknown[203.0.113.2]
plesk postfix/smtpd: warning: SASL authentication failure: realm changed: authentication aborted
plesk postfix/smtpd: warning: 203.0.113.2.example.com[203.0.113.2]: SASL DIGEST-MD5 authentication failed: authentication failure
- Plaintext authorization is disabled in Postfix:
# less /etc/postfix/main.cf | grep "smtpd_sasl_security_options"
smtpd_sasl_security_options = noplaintext
Outlook is not compatible with CRAM-MD5 authentication mechanism.