[CentOS] advice needed about "554 Too many recipients"

Bart Schaefer barton.schaefer at gmail.com
Mon Aug 17 00:03:54 UTC 2009

On Sun, Aug 16, 2009 at 3:50 PM, Rudi Ahlers<rudiahlers at gmail.com> wrote:
> A client of ours just requested to increase the max_recipients in Exim
> to 300, since he keeps getting "554 Too many recipients" error when
> sending a marketing email from MS Outlook.
> I would like to know, what are the implications of increasing the
> default 100 to 300? If 300 email recipients were added to the "To:"
> field, does it establish 300 connections to the SMTP server, or not?

Locally between Outlook and Exim, no, this won't establish more than
one connection to the SMTP server.  If Exim is acting as a smart
relay, it'll get one copy of the message with the whole list of
addresses in one transaction.

On the "other side" between Exim and the eventual recipients of this
mail, the likelihood is that Exim will make one or two connections per
destination domain.  If all 200+ recipients are at the same domain
(say, all yahoo.com addresses) then Exim may run into problems, but
it's not very likely.

However, if that list grows very much larger, both you and your client
are going to be a lot happier if the client stops attempting to send
out his own marketing mail with Outlook and instead engages a
reputable email service provider.  Assuming, that is, that he has
appropriately confirmed permission to send email to all those people.

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