[Mimedefang] md_check_against_smtp_server and md_graphdefang_log

[Les Mikesell]

On Tue, Mar 26, 2013 at 1:20 PM,  <kd6lvw at yahoo.com> wrote:
>
> You may not agree but that is what the function is for per the author.
> I agree that there are better ways (e.g. LDAP database) to do this than to fake an SMTP transaction, aborting just before the DATA phase.  When I first saw this function years ago, I thought that its purpose was to make callbacks to the sender's mailbox to test reverse deliverability, not to exclusively test the primary MX's acceptability of the message from a secondary.

It's not necessarily between a primary and secondary with public MX's.
  I found it very useful when the public MX's for a domain do not host
the actual users but instead relay through a private firewall to a
hidden internal delivery host.  However the inbound spam rate
eventually made it impractical - and I started maintaining virtusers
tables with a default reject rule on the MX hosts that sendmail can
process very quickly.

-- 
   Les Mikesell
     lesmikesell at gmail.com