"501 xxxx@problems.com ... Sender domain must exist" with qmail ?

[Olivier M.]

Hi,

I'd like that qmail check if incoming mail has a valid sender
domain : there are a lot of patches available on the qmail
webpage : which one would you recommend to me?

Are there some unwanted effects to reject mails using this
kind of method ? thanks for your hints & a nice week to you!

Olivier