I was in this world for like 8 years but switched to Thunderbird after one too many emails didn't send because I missed some notification or something in mu4e, and too many emails weren't rendering well in Emacs, and etc little problems that cropped up. I needed my email to Just Work, not be another aspect of my procrastination machi- sorry I mean, my IDE.
The need for email to Just Work is one reason I've never let emacs anywhere NEAR my email flow.
Everything in emacs becomes a Project.