i.Scribe is a small and fast email client with an integrated contact database and calendar.
It supports all the major internet mail protocols like POP3/SMTP/IMAP and uses international standards where possible.
i.Scribe doesn't require installation and can it be used from a removable drive without any reconfiguration. It comes with a bayesian spam filter and includes support for many different languages.
i.Scribe runs on Windows and Linux so you are able to take your mail with you even when changing operating systems. And don't worry about viruses, i.Scribe protects you from potential viruses and the usual security holes with its own virus safe HTML control and executable attachment protection.