nPOPuk is a free and portable email client created by Greg Chapman. It is a spinoff of nPOP, designed to allow users to carry their email on a USB flash drive. The client stores all data on the portable device, enabling email access and management on any compatible Windows system without installation.
Eudora is an email program produced by Qualcomm that is based on the open source Thunderbird client from Mozilla. Eudora portable is a reworked Thunderbird email client with a portable wrapper. The software utilizes a penelope news and mail extension or addon and comes packed with many features users might find in the Thunderbird mail client.
Quick Mailer (QM) is a Tiny Free Portable eMail Client. The eMail Tool is super tiny, fast and easy to use. Quick Mailer does allow attachments to be added to the messages as well. This tiny email client is perfect for situations where you just want to send messages or files without launching and setting up a large email client like outlook express.