It's generally considered good form to include a link to what you're talking about.
I thought about it, but based off previous experiences, most just search for it anyway. Here's the link:Mailpile
Typical email providers, like Outlook (hotmail), gmail, yahoo (do people still use that?), etc. are server
based, that is, everything is stored on a server and accessible via a browser. Outlook does have a local-side client, but it's got it's own gui I think. Mailpile has a web-coded interface without it's own window, so it opens up in your browser. The best thing about Mailpile is: you don't have
to put it through a browser. It's all open-source, mostly written in python, so you could just as easily implement a window to throw all the web-code into. Keep in mind, this is just the beta, so they may very well have plans to do that themselves.
As it is now, Mailpile supports SMTP and IMAP. They're working on implementing POP3, Tor, and SMTorPSend. Looks like it imports from most big e-mail providers, but I've only tested hotmail, which works fine, albeit very slow (took about 16-20 hours for 710 messages).