PostGrid has been great for automating our insurance mails for our client
Stannp - Stannp helps to create and send postal Direct Mail campaigns: letters or postcards.
Lob - A simple API to integrate print & mail solutions into your applications.
Postalytics - Automated direct mail software that’s faster, smarter & better. Postalytics sends personalized direct mail from your CRM and analyzes delivery & response.
Docsmit Mail - Send USPS Certified, Priority and First Class mail from Windows, Word or Web. API too.
Growmail Automated Direct Mail - Growmail enables businesses to send letters and postcards instantly through Automated Direct Mail.
KlientBoost - KlientBoost provides pay-per-click marketing and landing page solutions.