Have them use authenticated login, move to port 567 for their 
connections.  I believe you can set separate limits for authenticated users.

--
*Glenn Meadows*
/Mayfield Mastering
2825 Erica Place
Nashville, TN 37204
615-383-3708/

On 11/8/2011 4:06 PM, Frank Bulk wrote:
> We have customers (churches and schools, primarily), that have their own email server and want to send one email to hundreds of our customers.  They keep hitting up against the "Limit for recipients of untrusted channels, default g_rcpt_max", which we've set to 100.
>
> How do we overcome that in way that minimizes abuse by spammers?
>
> Frank
>
>