[cmer]

I personally would use it on top of something reliable like Fastmail. I mainly use Gmail over IMAP and it's painful slow and glitchy.

If what you're building could give me a great UI on top of Fastmail for when I want to use the web, and access to some kind of self-hosted archive, I'd probably go for it.

[jubari]

I pointed out further down, that my initial prototype ran completely on Dropbox. Right now, I backup all incoming mail instantly to Dropbox in JSON format for backup purposes.

I might want to look into a "on top of X"-solution. Thanks.