Symptoms
- On attempt to send an email via Microsoft Outlook, the login/password prompt appears and does not accept credentials.
- The warning below can be found in the
/var/log/maillog: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.
Resolution
- Login to the server via SSH.
-
Back up the file:
For CentOS/RHEL-based distributions:# cp /usr/lib64/sasl2/smtpd.conf /usr/lib64/sasl2/smtpd.conf.bak
For Debian/Ubuntu-based distributions:
# cp /etc/postfix/sasl/smtpd.conf /etc/postfix/sasl/smtpd.conf.bak
-
Disable Digest-MD5 authentication for postfix by editing
/usr/lib64/sasl2/smtpd.conffor CentOS or/etc/postfix/sasl/smtpd.conffor Debian/Ubuntu using a text editor and replacing the following line:mech_list: DIGEST-MD5 CRAM-MD5 PLAIN LOGIN
with
mech_list: CRAM-MD5 PLAIN LOGIN
-
Restart the Postfix service to apply changes:
# service postfix restart
