OT postfix multiple instances and recipient verification

Glenn Steen glenn.steen at gmail.com
Tue Oct 5 10:44:50 IST 2010

On 28 September 2010 10:13, Jason Ede <J.Ede at birchenallhowden.co.uk> wrote:
> I’m thinking of using multiple postfix instances to split up emails with
> multiple recipients (to make sure blacklisting and whitelisting works
> properly) and maybe to sign some outbound emails using domain keys…
> From what I’ve read on the postfix documentation I’ll have an inbound
> postfix instance that just passes all email on internally via a port I
> specify to the next instance where MS does its work and then sends it on to
> the destination server. All of this seems relatively straightforward so far.
> However, I use recipient verification to make sure we only accept emails
> that can be delivered. As the inbound postfix will not have any direct SMTP
> out then will this still work as it won’t be able to check where the emails
> are going to as it just passes all emails on to another port? I could put a
> transports file in place, but surely that would contradict a relayhosts
> setting in main.cf?
Eric is correct... The first instance has to know how the second
instance will route things, but without actually using that route
information... So that too is pretty straightforward:-).
> Also have others used multiple instances like this before with MS and what
> is the performance hit in having multiple instances? Are there any gotchas
> that I need to be aware of?
Well... The use of a second instance was the norm in the old days:-).
What you get there is a "static overhead" sort of, plus a per-message
overhead, but ... those are minor compared to the overhead incurred by
actually splitting mails/recipient (as long as the memory use doesn't
mak you start swaping, at least... No Alex, this is not the time to
reiterate the old "MS = swapping" joke...:).
I don't have any comparative statistics for you, but ... if you use
MailWatch, you should be able to deduce the impact on your gateways
and mailstore(s) by some smart use of SQL;-). The impact for a
single-store mailstore (like Exchange) can be huge, since the split
messages will be _new_ messages with new Message-IDs.
But as said, you can probably get a good picture of what impact it has
via log analysis.

I haven't had the time to ... freshen ... this up, and unfortunately
will probably not have any time to spend on it, in the near future at
least. Would be great if you could spruce up the wiki page a bit, when
you're done;-).

> Jason

-- Glenn
email: glenn < dot > steen < at > gmail < dot > com
work: glenn < dot > steen < at > ap1 < dot > se

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