> I have a question about qmail regarding its mail handling capacity.....
> How many remote emails can qmail send simulataneously, assuming it is run
> on a Dual-CPU PIII 500Mhz with 512Mb RAM and a SCSI hard disk? The
internet
> bandwidth is 10 Mbps.
>
> If I run 2 parallel processes that sends out emails, does it mean twice
the
> amount of emails get sent off simultaneously? if so, does that mean the
> more processes I run in parallel, the more emails get sent off at the same
> time? or will most of the emails get stored in the queue?
>
> What is the general number of emails that a machine with the above
> specifications can send per second/hour/day? How do I fine-tune it to send
> off millions? I only know of changing the "concurrencyremote" figure in
> /var/qmail/control/concurrencyremote. I set it to 100 for testing. What
> should be a good figure assuming that I will do free email hosting on the
> server for hundreds of thousands of users?
There are patches available that you will need to apply to achive maximum
throughput. You can find them on the qmail web page. One allows you to run
much larger queues efficiently by increasing the number of directoies the
queue is spread accross. Another allows increasing the maximum number of
concurrent remotes beyond 250. The patch allows up to 500 but that limit
seems to be linux related.
Set /var/qmail/control/timeoutremote to a number lower than the default. I
think the default is about 600 (10 minutes). I run it at 120 and have been
tempted to lower it to 60. A few weeks ago yahoo.com had a problem where
they I could connect to there smtp servers and then it would hand on there
side. This means that remote would sit around for the timeout period. 80
or 90 percent of my remotes were tied up in connections to yahoo.
I have played with removing flush statements from qmail-queue.c. This
dramatically increases the rate at which qmail-inject puts stuff into the
queue. This led to very large queues (my sending process backs off when the
queue gets to 100K messages). Overall throughput was not improved much.
Also if a box does crash then messages will be lost. My guess is your SCSI
drive makes this unneeded.
I currently run 6 qmail boxes set at 400 remotes. A PIII 650 with 512MB,
one IDE disk for the OS and another for /var/qmail gives me about 45-60 K
emails per hour. I had similar results with a Dual Celeron 500's but the
two boxes I had would crash about once a day. I don't know if there is a
problem with dual celerans or not. When I pulled the 2nd CPU out of both
boxes they became rock solid. They now get 30 to 40 K emails per hour.
Note my email mix is not random. We are sending newsletters / ezines. They
are typically 8KB in size and the individual boxes are sending and handling
bounces only. All other incomming email comes to another box setup for that
purpose.
