Squarespace Email Campaigns - Email, but pretty.
Hyperise - HYPERISE helps to create dynamic images that personalize to your email recipients and website visitors, on the fly.
Lob - A simple API to integrate print & mail solutions into your applications.
lemlist - Send emails that get replies 💌
PostGrid - Transform your Offline Communications. Use our fully-documented REST API to send personalized letters, checks, postcards and improve address accuracy.
OKZest - Mail merge for images. Increase click through rate in emails with automatically generated images.