Lob - A simple API to integrate print & mail solutions into your applications.
YetiForce CRM - Yetiforce helps companies best utilize free professional opensource CRM to lower costs and improve performance throughout the entire communication structure.
PostGrid - Transform your Offline Communications. Use our fully-documented REST API to send personalized letters, checks, postcards and improve address accuracy.
Sugar Sell - Sugar Sell is a customer relationship management and sales automation software that can be used by salespeople, marketers, account executives, and support teams.
AmazingMail - Business print-mail solution
Apptivo CRM - CRM for managing customer accounts