> shared memory?

As  in:  the GUI and the SMTP share a memory heap allocated to peering
information,  so  the  flow  between  the management interface and the
daemon is instantaneous. All that DNS would offer is a way of changing
peering  setups without the Imail GUI--not such a common occurence and
not worth the traffic.

> I  bet  99%  of  Imail  peer users have their all Imail peer servers
> directly onto internet as MX hosts.

Since we really can't debate statistics, maybe someone will pipe up.

> why? tcp connect to a peer, start smtp session, then either
> 
> VRFY user
> 
> or
> 
> RCPT TO: user
> 
> ... how is VRFY so much better?

Because it's really:

VRFY user

(response)

vs.

EHLO

(response)

MAIL FROM:

(response)

RCPT TO:

(response)

The only time that RCPT TO: is faster is if you only have two servers:
since  the  first peer attempt is always the only possible hit, so you
can afford to have the whole conversation at once without a pre-flight
check.  With  more and more servers, you're wasting mucho bandwidth by
having  three-part  convos  just  to  get rejected. (Yes, HELO/EHLO is
optional,  which would save you one part, but it's gonna look messy in
your logs to have last-hops with no hostname.)

Sandy


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