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

Rudi Ahlers rudiahlers at gmail.com
Sun Aug 16 22:50:32 UTC 2009

Hi all,

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.

Before you tell me to use Pine / Mutt / etc to send plain-text emails
via mailman, this isn't an option.

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?

In the Exim documentation
I found this:

"If this option is set greater than zero, it specifies the maximum
number of original recipients for any message. Additional recipients
that are generated by aliasing or forwarding do not count. SMTP
messages get a 452 response for all recipients over the limit; earlier
recipients are delivered as normal. Non-SMTP messages with too many
recipients are failed, and no deliveries are done.

Note: The RFCs specify that an SMTP server should accept at least 100
RCPT commands in a single message."

But, this doesn't tell me if it will have a performance issue with the
server, or if other mail servers will have problems with our mail
server sending the email to so many recipients in one go.

Can someone give me some pointers on this one?

Kind Regards
Rudi Ahlers
CEO, SoftDux Hosting
Web: http://www.SoftDux.com
Office: 087 805 9573
Cell: 082 554 7532

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