I agree.  There doesn't seem to be a way to limit recipients/second.  That would be useful.

At 10:57 AM -0400 5/1/08, Valdis Kletnieks wrote about Re: Experience with Rate Limits:
>On Thu, 01 May 2008 07:22:49 EDT, Bill Verity said:
>
>> VMS: SMTP_RATE_LIMIT "12Mbps"
>>   unix: SMTP_RATE_LIMIT="12Mbps"
>>   export SMTP_RATE_LIMIT
>>   Win:SMTP_RATE_LIMIT=12Mbps
>
>Unfortunately, unless your actual upstream network connection is congested
>(in which case you probably have a bigger problem), limiting the bandwidth
>usually doesn't impact performance anywhere near as much as limiting the
>number of recipients/second (especially if you have a large mailing list
>sent to a lot of sites) - the TCP 3-packet handshakes and the first few SMTP
>round/trips (EHLO/MAIL FROM/RCPT TO) end up dominating the network traffic,
>especially if the remote site doesn't advertise the ESMTP PIPELINING extension.
>
>Phrased differently - a 4K E-mail to 5,000 users usually ends up "costing" almost
>the same as a 40K E-mail to 5,000 users, and 4K to 5,000 users "costs" a lot
>more than 40K to 500 users...


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Bill Verity - 814-865-4758  Fax: 814-863-7049
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