[Assp-user] spammer@notexistentdomain.com

[Marrco <as...@mi...>]

after the

/^\d+\.\d+\.\d+\.\d+$/          REJECT fake IP literal in HELO hostname
/^[^\.]+\.?$/                   REJECT unqualified HELO hostname

regex helo filtering proposal for ASSP, what about a check for non existent
domain ?

It's not good practice to accept an email with an invalid sender domain. I
think a dns query for the MX record of the sender domain is all we need for
such a test.