[Mimedefang] Mail volume control

[NFN Smith]

My site is running a server setup where we have sendmail 8.12.10 and 
MIMEDefang 2.25-1.  (Yes, I know that the copy of MD is old).

In our setup we do quite a bit of work with MD in rewriting our headers, 
as a way of masking domains that we use only internally.  One of the 
effects of this is that when the rewriting is done, a message with 
multiple recipients is generally broken apart at the time of rewriting, 
so that there is one copy of the message per addressee.

Where we're having occasional problems is when we have users who do 
large personal mailings, sometimes as many as 400 or 500 recipients on a 
single message.  When this happens, it makes a major hit on server 
performance.  A similar difficulty we had a couple of weeks ago is a 
user that sent a message to only about 75 addressees, but each copy of 
the message had a 3 1/2 MB attachment.  That one brought the server to 
its knees, and I believe that we eventually had to reboot to get 
sendmail and MD totally cleared.

I don't admin that server directly, so I don't have a better detail of 
the exact symptoms of what all went wrong.

What I want to find out about is how we can do a better job of filtering 
by size -- is that something to do in sendmail directly, or something to 
do with MIMEDefang?

Specifically, there's a couple of things we would like to be doing:

1) Set a simple maximum number of recipients that a message can show in 
either To: or Cc: lines.

2) Set a "maximum batch size" -- essentially the product of size of 
messages and number of addressees.  A short message (e.g. 5K) with a 
larger number of addressees is less of a problem than a longer message 
(e.g., several hundred KB) with fewer addressees.

Thanks in advance for responses.

Smith