PostGrid has been great for automating our insurance mails for our client
Mailform - Mailform is the easiest way to print and mail documents online.
Lob - A simple API to integrate print & mail solutions into your applications.
Click2Mail - Mail outsourcing on-demand.
Postalytics - Automated direct mail software that’s faster, smarter & better. Postalytics sends personalized direct mail from your CRM and analyzes delivery & response.
EZGram - The EZGram web site makes it easy to create custom letters that can be sent anywhere in the world.
AmazingMail - Business print-mail solution