At work we use an external spam filtering service. I want to avoid that for our internal/private servers.

Mail is redirected to the spam filtering service through our name server MX records and from the filtering service to our public facing mail server (postfix/dovecot).

Currently emails from our own internal/private servers also go through the spam filtering service.

I trust emails from our internal/private servers and do not want to use the spam filtering service. Another reason is security. Internal server emails should not be going through any kind of external servers.

Some searching reveals possible directives:

smtp_dns_support_level = disabled
lmtp_host_lookup = native
smtp_host_lookup = native

Using those directives my test system wants to send emails to our domain web server rather than our mail server. My guess is I need to configure the test server to know that the default mail server is mail.mydomain.com rather than presume www.mydomain.com.

I tried modifying mydestination = mail.$mydomain, $myhostname, localhost.$mydomain, localhost

mydomain is defined correctly in main.cf.

The mail server IP address is in /etc/hosts.

What am I missing?

Thanks again.

I tried transport maps with no success. I think the problem is the mail server is configured to refuse direct incoming mails and is configured to divert all mails to the spam server.