It’s not a secret gmail is very popular not only because they offer a lot of space, it’s also very fast, simple and flexible, and it indexes everything in it’s own style. It really rocks when you have a lot of email correspondence like me and have to search mail archives often.
ZOE (actually it’s ZOË) is a tool that offers same gmail-style indexation of all your mail - but locally on your computer. It’s actually a email client, but it also acts like a simple mail gateway or server, means you can easily use your favourite email client like Outlook easily with it.

It’s so flexible - wow, you can even read your mail accessing by FTP client, web client, imap, pop3 - any way you can imagine it. It’s also pretty quick, you can find details on it’s official site.

It is more flexible solution than Neo Pro, it only works with Outlook with it’s base, while ZOE is much more powerful, it’s like a gmail server on your computer. Please don’t hesitate trying it.