Austad, Jay:
> Right now, I'm using ezmlm with qmqp modifications that will balance the
> load between multiple qmqp servers, if I run out of outbound capacity, I can
> just add more qmqp servers (qmail).

Postfix has a qmqp server. It is in daily use for bugtraq and
other securityfocus mailing lists.

The Postfix qmqp server supports qmail-style VERP return addresses.

> I'm planning on replacing the ezmlm/qmail list server box with a
> postfix/smartlist setup. I'm planning on having postfix send all outgoing
> mail to my "splitter" box, which forks off the outgoing mail to several
> qmail QMQP servers (I'm keeping these). I'm choosing smartlist because it
> uses the choplist program which will split my outgoing lists up into many
> messages grouping addresses for the same domain into one message, and with
> multiple messages, my load balancing mechanism will have a little bit more
> uniform distribution.
>
> Here are my questions:
>
> 1. Say I have 4 smarthosts, can I specify all of these smarthosts in the
> postfix config and have it relay messages to them randomly to load balance
> between them? I'd like to dump the qmail stuff completely, but right now, I
> can pipeline messages into my splitter box, and it will randomly distribute
> them nicely to all of the qmqp servers.

If you provide one DNS record with 4 addresses, then Postfix will
randomize the connections. Code from Elias Levy of Securityfocus :-)

> 2. Say I have a single message with 1000 aol subscribers as recipients,
> will postfix open one connection and just send across the one message with
> all of those recipients, or will it send multiple messages? How about if I
> have 1000 separate messages all to AOL subscribers, will it open one
> connection and pipeline, or 1000 separate ones?

Postfix sends 50 recipients per connection (the number is configurable)
and makes as many parallel connections as it is allowed to make.

The settings are:

    default_destination_recipient_limit = 50
    smtp_destination_recipient_limit = $default_destination_recipient_limit

However, with VERP style return addresses Postfix makes one connection
per recipient.

> 3. What should I keep in mind when setting up/compiling postfix on the main
> list server? Is there anything special I need to do to increase the
> performance of the queue? (my qmail box is getting hammered because of the
> size of the queue) Can I easily change the amount of time a message is
> allowed to be in the queue? (many of our mailings are time sensitive)

It should work with defaults. They are biased towards large machines.

By design, Postfix does a lot less disk I/O than qmail, so that
should make a difference.

> 4. What is the maximum number of outgoing concurrent connections I can
> possibly have? I saw that you have to do a -DFD_SETSIZE=xxxx when compiling
> to get enough threads. But under freebsd 4.4, do you also have to recompile
> the kernel to make it work correctly when doing a lot of connections?

See http://www.porcupine.org/postfix-mirror/faq.html#moby-freebsd.

        Wietse
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