Postfix: how to verify sender's MX record

is it possible to configure Postfix to verify the sender's MX record?

For example: if a mail comes in from some.sender@example.com it should look up the MX record(s) for example.com and verify that the sending mail server is listed in the MX records.

Is this possible and does it make sense to block spam mails? Or is there another way to stop spam mails pretending to come from trustworthy domains?

Thanks!
Oliver

Answer

A word of warning:

An MX record provides information about where email should be delivered. It does not necessarily provide any information about where email originates. It is entirely possible -- even likely -- that mail will be coming from a system that is not listed as an MX for the given domain.

SPF records, on the other hand, allow you to verify that email is being sent by a system that is an authoritative sender for the domain.