reject_unknown_sender_domain behavior

[Paul Enlund]

Hi

I want to stop MAIL FROM: someb...@[a.b.c.d] (IP address) being accepted.
My impression would have been the config below would do this as say [1.1.1.1]
does not have A or MX records.
smtpd_sender_restrictions =
        reject_unknown_sender_domain


How can I achieve my goal.

Regards Paul Enlund.