[exim] Ultimate spam defense - check for the sender MX recor…

Hello,

I would like to increase a spam defense of our server by checking if a
sender really represents an MX server of his/her organization. So if a
certain PC is trying to send me an e-mail from user@??? then we
will check if this person's IP address is within MX servers of
domain.com, otherwise we'll refuse to accept the mail.

Is it feasible? How can I achieve this?

With respect and happy holidays

Artem