SpamCheck from Postmarkapp allows you to process the spam score of incoming or outgoing email messages, without the hassle of managing SpamAssassin. You can also utilize their light-weight JSON API to use SpamCheck in your own apps.
Fractal Validates your HTML email across all the major email clients (i.e. Gmail, Hotmail, Outlook, Lotus Notes) and automatically fixes known email quirks and issues. The report also details fixes not applied to your code. Supports over 24 email clients and 100 CSS properties.
Traffic Attractor - Mailing List Manager V1.1 Traffic Attractor - Mailing List Manager V1.1 (2.5 MB) is a freeware tool to create, maintain and mail to a mailing list. Includes POP email address authentication.