Download Software Mozilla Thunderbird Portable Version

It's a highly customizable email client with an intuitive user interface. Highly expandable through add-ons." I was surprised by how quickly it works and how easily it interacted with my online email provider (Gmail). It made a complete copy of my Gmail account and checked for any new messages regularly. The interface is very easy to navigate, considering it's just like Firefox (and that happens to be my main browser).

That said, it's not a light application and some extensions may not be portable. If you want a lightweight email client to run from the tray and just check your mail, then POP Peeper is an excellent option. See these steps to have POP Peeper store your data in its own folder. Another option is to set it to never store data to the disk, or manually enter its "data" folder path in the storage options.