Limitations on outgoing email messages are enabled on the server, but don't work for
Outlook is configured for outgoing email authentication with user name in UPN format (email@example.com)
Outlook keeps sending local part of user name instead of user name in UPN format:
csp12 postfix/smtpd: 97D2D101AFA: client=servername.domain.tld[188.8.131.52], sasl_method=DIGEST-MD5, sasl_username=user
The issue is specific to
Outlook . Please contact Microsoft regarding this issue.
Note: in case of using
Outlook 2007 , please, check the following article .