In my main.cf I have sender_dependent_default_transport_maps = tcp:localhost:6002
and in my master.cf I have: 10025 inet n - n - - smtpd -o syslog_name=postfix/10025 -o content_filter=scan:[127.0.0.1]:11125 -o receive_override_options=no_address_mappings scan unix - - n - 10 smtp -o syslog_name=postfix/scan -o smtp_send_xforward_command=yes -o disable_mime_output_conversion=yes -o smtp_generic_maps= [127.0.0.1]:11126 inet n - n - 10 smtpd -o syslog_name=postfix/11126 -o content_filter= -o receive_override_options=no_unknown_recipient_checks,no_header_body_checks,no_milters -o smtpd_helo_restrictions= -o smtpd_client_restrictions= -o smtpd_sender_restrictions= -o smtpd_recipient_restrictions=permit_mynetworks,reject -o mynetworks=127.0.0.0/8 -o smtpd_authorized_xforward_hosts=127.0.0.0/8 microsoft365 unix - - n - 10 smtp -o syslog_name=postfix/microsoft365 -o smtp_sasl_auth_enable=yes -o smtp_sender_dependent_authentication=yes -o smtp_sasl_password_maps=tcp:localhost:6001 -o smtp_sasl_security_options=noanonymous -o smtp_sasl_tls_security_options=noanonymous -o smtp_tls_security_level=encrypt My content filter is on port 11125 and returns the email back into postfix on port 11126. For the sender in question my sender_dependent_default_transport_maps returns microsoft365:[podxxxxx.outlook.com]:587 My understanding is that mail coming in on port 10025 should first go to the content_filter scan:[127.0.0.1]:11125, my filter should scan it, gets reinjected on port 11126, the the default_transport from the sender_dependent_default_transport_maps should use the microsoft365 transport. When I have sender_dependent_default_transport_maps in main.cf my content_filter is never calls. The mail comes in on port 10025 and goes straight to the microsoft365 transport. Without the sender_dependent_default_transport_maps mail does hit my content_filter. Am I not understanding how content_filter should work? I tried to use sender_dependent_relayhost_maps and it did call my filter. How do I chose different transports based on the relayhost?
