Squarespace Email Campaigns - Email, but pretty.
Drip Scripts - Create automated email sequences in 60 seconds
Lob - A simple API to integrate print & mail solutions into your applications.
Polymail Sequences - Simple, powerful multi-stage email campaigns
PostGrid - Transform your Offline Communications. Use our fully-documented REST API to send personalized letters, checks, postcards and improve address accuracy.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.