Author: Marc Perkel Date: To: Exim User's Mailing List Subject: [exim] Alternate callout verification sequence suggestion
According to the docs - this is the sender callout sequence:
For a sender callout check, Exim makes SMTP connections to the remote
hosts, to test whether a bounce message could be delivered to the sender
address. The following SMTP commands are sent:
HELO </primary host name/>
MAIL FROM:<>
RCPT TO:</the address to be tested/>
QUIT
May I suggest something different.
HELO </primary host name/>
250 helo MRLRY
MAIL FROM:<>
501 bogus mail from
# fail detected - try different address
MAIL FROM: <some real email address - possibly the To: header?>
250 OK
RCPT TO:</the address to be tested/>
QUIT
This would also return a flag set indicating that the domain rejects
null senders.