It sounds as if you want something like SPF and a policy daemon. Just google it.
- Accept external SMTP traffic only from MX hosts James B. Byrne
- Re: Accept external SMTP traffic only from MX hosts Larry Stone
- Re: Accept external SMTP traffic only from MX host... Ron Wheeler
- Re: Accept external SMTP traffic only from MX ... Ron Wheeler
- Re: server side postfix tactics. Ron Wheeler
- Re: Accept external SMTP traffic only from MX ... Joey J
- Re: Accept external SMTP traffic only from MX ... Ron Wheeler
- Re: Accept external SMTP traffic only from MX hosts Lewin Bormann
