Ordering of received vs. delivered messages

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Ordering of received vs. delivered messages

Jérôme Oufella-2
I have a question regarding the queue handling methods in Postfix.

Is there a way to guarantee that messages that come in through the
smtpd(8) server, will be delivered to local mailboxes in the exact
same order by the local(8) delivery agent ? Under normal, but also
non-normal times, heavy incoming traffic for example.

Also, I have the same question if the message destination address is a
virtual alias, that points to several destinations, let's say 1 local
and 1 remote. Will a busy remote defer the delivery of the local
recipient of the message ?

Thanks for your hints.

Jerome
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Re: Ordering of received vs. delivered messages

Victor Duchovni
On Mon, Jul 28, 2008 at 11:51:20AM -0400, J?r?me Oufella wrote:

> I have a question regarding the queue handling methods in Postfix.
>
> Is there a way to guarantee that messages that come in through the
> smtpd(8) server, will be delivered to local mailboxes in the exact
> same order by the local(8) delivery agent ? Under normal, but also
> non-normal times, heavy incoming traffic for example.

No, but if the system is not too busy, and the incoming queue is serviced
by qmgr(8) in a timely fashion, the delivery to any single mailbox will
be approximately time-ordered.

> Also, I have the same question if the message destination address is a
> virtual alias, that points to several destinations, let's say 1 local
> and 1 remote. Will a busy remote defer the delivery of the local
> recipient of the message ?

Postfix performs delivery to different destinations separately and in
parallel.

For two nexthops sharing the same transport, until the transport
process limit is reached, one congested nexthop will not slow down
another congested nexthop. With default process and concurrency limits,
no *single* slow nexthop will saturate the transport process limit.

Until the active queue is saturated, one congested transport will not
stall delivery for another transport.

Do read QSHAPE_README.

--
        Viktor.

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Re: Ordering of received vs. delivered messages

Wietse Venema
In reply to this post by Jérôme Oufella-2
=?ISO-8859-1?Q?J=E9r=F4me_Oufella?=:
> I have a question regarding the queue handling methods in Postfix.
>
> Is there a way to guarantee that messages that come in through the
> smtpd(8) server, will be delivered to local mailboxes in the exact
> same order by the local(8) delivery agent ?

There is no first-in/first-out guarantee, except when the queue is empty.

> Under normal, but also
> non-normal times, heavy incoming traffic for example.
>
> Also, I have the same question if the message destination address is a
> virtual alias, that points to several destinations, let's say 1 local
> and 1 remote. Will a busy remote defer the delivery of the local
> recipient of the message ?

Postfix schedules local and smtp deliveries in parallel.

        Wietse