> I had a script that piped to curl to send, Mail.app for downloading via POP and Vim to read/write

Wow, this is very interesting, and I might even try it at some point. It might have been a bit challenging to sync and read the emails though, but the sending part seems nice.

Was the reason for why you gave up related to syninc emails?

I liked that Mail.app stored every message as a single separate file, instead of the mbox that Thunderbird and others did. But at some version they started saving a hash with a multiple folder structure and that broke the setup. I had a few issues with MIME encoding as well, which were probably my fault. It was too much work and I eventually gave up, but if I find the will to do it again, I'd choose a simple POP downloader + some filter (if not in address book or previous recipients, move message to “Unknown”).

qlmanage worked great for HTML messages and attachments, though.

FYI, the maildir format (usable with mutt and numerous other email clients) also saves each email message as an individual file, and avoids mbox's notorious quoting issue.

<https://en.wikipedia.org/wiki/Maildir>

You might find vim-anywhere what you need. Roughly speaking, in almost any text-entry field you can hit a hotkey, get a temporary macvim buffer, and when you wq the contents are pasted where you came from.

https://github.com/cknadler/vim-anywhere