[Mailman-Users] how are large distribution lists handled

Jon Carnes jonc at nc.rr.com
Thu Jul 3 17:58:20 CEST 2003

Check out the archives for reams of discussions on this setting.

Basically it lets mailman drop off a bunch of mail all destined for the
same domain in one email.  If 500 of your list members are all with
AOL.com then Mailman will put all 500 addresses into one email and dump
it out to your MTA.  What your MTA does with it is up to it.

This dumps the mail as quickly as possible out of Mailman and into your
MTA for delivery.  That's why most folks like the value to be high.

Your MTA also has some settings that affect how many recipients an email
is allowed to have.  If you keep it at 500 for dumping mail to aol, then
your mail will get bounced.

On sites using sendmail, I find that the best value for SMTP_MAX_RCPTS
is between 5 and 10.  This delivers the mail rapidly in small chunks and
doesn't set off any alarms at various Domains.

Play with it yourself and see what works for you.

I've seen ancient graphs of delivery times vs number of user on lists,
mapped for various levels of SMTP_MAX_RCPTS.  For that site, the best
value to use was 5 (for delivering mail the fastest).

Jon Carnes

On Thu, 2003-07-03 at 10:10, Bruce Embrey wrote:
> Mailman-Users:
> I am using Mailman 2.1.1 I have several lists and my setting for 
> SMTP_MAX_RCPTS = 500. If I have a list with 4000 addresses will this 
> setting segment the message into 8 messages with 500 recipients per 
> message? This SMTP_MAX_RCPTS = 500 was the default setting when I installed 
> it. Is it the recommended setting or should it be changed?
> Bruce Embrey
> Bruce Edward Embrey : VMS Systems Manager
> Campus Email Admin : UNIX / Linux Administrator
> Hood College : embrey at hood.edu : Phone (301)696-3927
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