[Mailman-Users] Max Number of Addresses in Lists

J C Lawrence claw at kanga.nu
Tue Dec 4 19:46:47 CET 2001

On Tue, 4 Dec 2001 10:50:22 -0600 
Jeffrey M Kenton <jkenton at iastate.edu> wrote:

> I just got off the phone with the director of external
> information for my college. She wants to know if our existing
> system (Mailman) will handle lists that contain "between 4500 and
> 7000 email addresses." 

Not a problem.

> This potential number of emails far exceeds, by a considerable
> amount (~5x), the number of email addresses on the largest list
> that I currently maintain. I do not have any fear that the
> individual components in the chain (mailman and sendmail) can
> handle the load, but I wonder about the hardware I might need.

I'd start out by suggesting that you may want to choose another MTA:


> I imagine that there will also need to be a significant amount of
> tweaking to my sendmail configuration to allow it to efficiently
> handle a sudden request to handle up to 7000 outgoing emails. The
> emails will also have attachments, most probably, and could be
> very large (~300K each). Approximately 200MB of outbound bandwidth
> per message to those lists is a frightening specter...

Fundamentally MTAs are disk IP bound.  I wouldn't worry about it.
Your system is going to thrash when Mailman's qrunner delivers the
initial set of messages to the local MTA for delivery, but from
there it should be fine.

  1) Exim may be specifically recommended here as by default it has
  very local-system-load protecting behaviour.

  2) Typically setting SMTP_MAX_RCPTS (number of RCPT TO's per
  message) to a value between 5 and 10 gives the best performance in
  terms of parallelisation and delivery time.  However in your case
  that also means a fairly large number of spool entries to be
  created for each mailing.  You may want to sacrifice delivery
  performance for system IO load by setting SMTP_MAX_RCPTS higher.

> If someone who reads this list has set up such huge volume lists,
> could you please respond to me directly as well as this list so I
> can pick your brain a little?

Actually you're talking about a rather small list.  Get up close to
or past the 100K point and it gets really interesting (the largest
known list has 1.3M subscribers).  This reply is on-list.  Feel free
to continue the discussion off-list if you wish, tho I think it
would be better here.

J C Lawrence                
---------(*)                Satan, oscillate my metallic sonatas. 
claw at kanga.nu               He lived as a devil, eh?		  
http://www.kanga.nu/~claw/  Evil is a name of a foeman, as I live.

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