Mailmeteor - Send hundreds of personalized emails with Gmail.
GMass - GMass allows you to easily schedule emails, send out mass emails and mail merge campaigns and more with Gmail! Click here to learn about more features!
Mailazy - Modern Email Delivery API
Trumail - Free email verification API
ZeroBounce - Removes invalid emails from your list to prevent email bounces from ruining your deliverability.
Vero Newsletters - The first "baseless" email marketing tool.