Blocking port 25 traffic for spam purposes

Since our iSeries is our mail server, I have permission from On High to post
this to midrange-l <g>.

We started using CleanMessage to intercept and eliminate as much spam as
possible.  It's working great, stopping 95% of the spam.

The last 5% is spam being sent directly to our IP address instead of
properly using the MX record.

Someone on this list suggested blocking port 25 from all IPs _except_
CleanMessage.  Anyone doing this?  Working OK?  Downside?  I assume only
spammers would be trying to bypass/ignore the MX record.

Oh, and if we do block that port, can a company laptop, via VPN, still
handle email OK?  I'm going to try that from home tonight.

Thanks.

-- 
Jeff Crosby
Dilgard Frozen Foods, Inc.
P.O. Box 13369
Ft. Wayne, IN 46868-3369
260-422-7531

The opinions expressed are my own and not necessarily the opinion of my
company.  Unless I say so.