On Tue, Sep 29, 2020 at 3:33 PM Wietse Venema <[email protected]> wrote: > Then use check_recipient_mx_acces?
Yes, after some pretty thorough testing, check_recipient_mx_access seems to be the perfect fix for our situation. The message gets refused and the MUA gets a 554 error message. For reference here are the findings from the other options: check_recipient_a_access bounces mail for a domain simply for being web-hosted in that IP block, even if that domain does have valid email service somewhere else, which is not desirable in this situation. reject_unverified_recipient returns a temporary initial fail if the domain has not yet been verified. Most of the client applications using this server don't appear to be able to queue and retry, so that wasn't a good fit either. Thanks again, Wietse & Bill. Postfix really is a wonderful tool!
