Outlook fails to send a mail: SASL authentication failure

Created:

2016-11-16 12:51:32 UTC

Modified:

2017-08-08 13:09:59 UTC

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Outlook fails to send a mail: SASL authentication failure

Applicable to:

  • Plesk for Linux

Symptoms

When trying to send a mail from Microsoft Outlook the login/password prompt appears and do not accept the credentials. The warning as below is in the server mail log /usr/local/psa/var/log/maillog :

Aug 17 12:03:18 mail.example.com postfix/smtpd[17318]: warning: SASL authentication failure: realm changed: authentication aborted

Cause

Current implementation of a DIGEST-MD5 authentication in libsasl2 library is incompatible with Microsoft Outlook. Additional details can be found at: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=603118

Resolution

Disable Digest-MD5 authentication for postfix:

1. Back up the file /usr/lib64/sasl2/smtpd.conf
2. Edit the file /usr/lib64/sasl2/smtpd.conf with replacing there a line mech_list: DIGEST-MD5 CRAM-MD5 PLAIN LOGIN with mech_list: CRAM-MD5 PLAIN LOGIN
3. Run the following command to check whether Postfix configuration is valid:

# /etc/init.d/postfix check

4. Reload Postfix to apply changes:

# /etc/init.d/postfix reload

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