HI B.R. thanks for responding.

1) smtp_auth none + xclient off:
Outlook client cannot authorize,
Emails from outside can be received
Telnet without manual auth login: Relay Access denied
Telnet with manual auth login: Relay Access denied

2) smtp_auth set + xclient on
Outlook client can authorize, in mail.log: sasl_method=XCLIENT, sasl_username=username@mydomain.de
Emails from outside cannot be received: : 530 5.7.1 Authentication required (in reply to MAIL FROM command)
Telnet without Manual auth login: Right after mail from: 530 5.7.1 Authentication required
Telnet with manual auth login: login possible, email send possible. in mail.log: sasl_method=XCLIENT, sasl_username=username.de

Pls note the difference in sasl_username!

Cheers,
Cugar15