Squarespace Email Campaigns - Email, but pretty.
Lob - A simple API to integrate print & mail solutions into your applications.
Click2Mail - Mail outsourcing on-demand.
PostGrid - Transform your Offline Communications. Use our fully-documented REST API to send personalized letters, checks, postcards and improve address accuracy.
Sendoso - Sendoso’s B2B engagement platform helps companies accelerate sales and retain customers with gifts and rewards.
PebblePost - PebblePost invented Programmatic Direct Mail® to transform real-time online activity into personalized, dynamically rendered direct mail.