Not to sure about spiffs I know there is some pay off if you resell their services, but you can get excellent service from any of the following:
eOutlook:
www.eoutlook.com
Mailstreet:
www.mailstreet.com
Intermedia:
www.intermedia.net
Lanlogic:
www.lanlogic.com
Bell Hosted Exchange:
http://hostedmail.bell.ca/products.html
All the above offer Exchange E-Mail and BES