[Mailman-Users] Number of Recipients

Mark Sapiro mark at msapiro.net
Fri Jun 24 11:41:08 EDT 2016

On 6/24/16 2:44 AM, Julian Kippels wrote:
> I have a question regarding the number of recipients per mail. If I have
> a list with 50 entries, does mailman send one mail with 50 recipients,
> or 50 mails with one recipient each?

It depends. With completely default settings Mailman will send the mail
in chunks of up to 500 recipients per message, but the chunks are
grouped in four groups by top level domain with the .com domains in one,
the .net and .org domains in a second, the .edu, .us and .ca domains in
a third and the rest in a fourth.

So there will be up to 4 messages with the .com addresses in one, the
.net and .org addresses in another and so on.

But, things like personalization and VERP will cause the messages to be
sent individually, so 50 messages with one recipient each, and chunks
are limited by SMTP_MAX_RCPTS which can be smaller than 500.

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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