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Re: 400 000 mails in 12 Hours

On Thursday 27 February 2003 06:10, debian-isp wrote:

> I have the task of setting up a mailserver capabel of sending 400 000 mail
> in a max time of 12 hours. All mails have an attachment of 1 mb. The system
> should be a mailer for a newsletter system. As I made quite a couple of
> things with postfix, my concern is the amount and considerations which have
> to be made when handling such an amount.

Do not personalize the emails then they can be sent to multiple recipients at 
once.  I have used mailman on postfix and majordomo on both postfix and 
sendmail, no matter the combination you will see that emails to people at the 
same domain will go out as a single email.

With 400,000 emails there will be thousands of people at the same domain for 
every email that you send.  Postfix by default will try to send emails in 
chunks of 50 recipients before breaking up the remainder into smaller chunks.  

Your 400,000 deliveries could be reduced to 50,000 lets say (number pulled 
from thin air with no statistics to back it up).

Whatever MTA you use I'm sure you'll need to do some tuning.  We had a default 
postfix install that would choke when it had 1,000 messages in the queue.  It 
would take up to 3 hours to deliver an email that should have been instantly 
delivered.  Now that we've tuned that client's postfix a bit it instantly 
delivers messages even when there are 2 to 3 thousand messages in the queue, 
and without noticable load being added to the machine.

The above system has a majordomo list of about 4,000 subscribers.  During the 
10 minutes immediately after the list gets sent the system managed to send 
4,784 emails .. that's over 7 emails per second.  549 of those emails were 
delivered to localhost or other servers on the localnetwork.

To summarize this machine was able to send over 7 messages per second to 
remote email address.  Exrapolating that over 12 hours you could have 302,400 
emails delivered.  This machine is a P3-700, 512MB RAM and single IDE disk, 
it is not a powerhouse and it is barely taxed (by feel only) during this 
mailing.  The Internet connection is an already saturated and poorly 
performing 1mb SDSL.  The email that I grabbed these statistics from was 
approximately 7KB.

As someone else has pointed out you shouldn't really send large attachments by 
email.  The 1MB becomes typically 30% larger, better to have them click on a 
link to the document at their leisure.

Also many people won't appreciate your mass mailing large files particularly 
the network admins whose bandwidth, virus scanners and other resources that 
you are clogging up.

With 400,000 emails you will end up with a tonne of undeliverable emails in 
your queue, you will have to have the bounce handling, queue aging and all 
such parameters very well set up beforehand.  With a good machine and 
reasonable bandwidth I don't think the task should be that difficult although 
since I haven't handled such load I can't say for sure.

If you're emails are text only I doubt you'll have any problem coming up with 
a postfix config that blasts them out even faster than you need.

Fraser Campbell <fraser@wehave.net>                     http://wehave.net/
Brampton, Ontario, Canada                        Linux 2.4.20 AuthenticAMD

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