Make it possible to use a Template and a spreadsheet to batch-send emails with open / link tracking. Nylas Mail used to have this feature but the implementation confused users and didn’t handle sending errors well. The new version will do these things better.
(From the roadmap)
Related Issues:
Great! This was a feature I was using and appreciating back in the days with Nylas and I was looking for it in Mailspring. To me, the usage was not confusing; actually I remember it as quite elegant. And it makes perfect use of mailspring’s templating system.
Is mail merge working? How do you do this?
Hello again! 
3 Years later, I’d still love to see this still unmatched feature from N1 resurrected! Or did i miss something and it’s aready implemented because it has the accepted tag?