We use our website which is a secure login for our clients created in PHP. We send special requests to our registered clientele through the website using php mail. One email is generated that add the selected clients to a BCC list. This list could be 200+ at times.
My exchange server can handle all the traffic, my concern is will this much activity be blacklisted as spam or for mass emailing?
We do this alot, and we also send a update each night to all registered clientele of changes or updates to our site.