PostGrid has been great for automating our insurance mails for our client
Lob - A simple API to integrate print & mail solutions into your applications.
AuthSMTP - AuthSMTP is the outgoing SMTP email service for e-commerce websites, mailing lists or email applications.
Postalytics - Automated direct mail software that’s faster, smarter & better. Postalytics sends personalized direct mail from your CRM and analyzes delivery & response.
Sparkpost - Deliver your app and website emails on time and to the inbox. Trusted to send 25% of the world's non-spam email. Email delivery for companies big and small.
AmazingMail - Business print-mail solution
BriteVerify - Email Validation & Email Verification reduces bounce rates up to 98%. Rapidly verifying email addresses has never been easier, just drag drop and deliver!