Hello, I am replying to myself, because I found the problem:
> smtp inet n - - - - smtpd > 25025 inet n - - - - smtpd > -o smtpd_tls_auth_only=no > -o smtpd_sasl_auth_enable=yes > -o smtpd_sasl_security_options=noanonymous,noplaintext > -o smtpd_sasl_local_domain=xxxx > -o broken_sasl_auth_clients=yes > -o smtpd_client_restrictions=permit_sasl_authenticated,reject > -o > smtpd_recipient_restrictions=permit_sasl_authenticated,reject_unauth_destination > -o content_filter= Here ^^^^^^^^^^^^^^^^^ I turned off the content_filter which is not needed for the SMTP AUTH submissions. I overlooked though that I had specified receive_override_options = no_address_mappings in main.cf so virtual mapping would not occur before the content_filter, and thus never for the additional smtpd listening on 25025. After adding a line -o receive_override_options= to it in master.cf now everything works as expected. Kind regards, Ch. Scheurer