Here's the story:

Beam (BEware, Another Mailer) is an open source e-mail client for BeOS (R5 and onwards) that aims to be fast, stable and feature-complete.

Beam was created by Oliver Tappe and is copylefted by means of the GPL.

So what does Beam currently offer?

• Multiple Mail-Accounts (POP & SMTP), with support for default-acounts and automatic selection of appropriate account when replying, etc...
• Fully MIME compliant (Beam passes the MIME-Torture-Test)
• Performance adequate for large mail-folders (>10000 msgs), with optional mail-caching
• POP-authentication (POP3, APOP, CRAM-MD5, DIGEST-MD5)
• SMTP-authentication (SmtpAfterPop, PLAIN, LOGIN, CRAM-MD5, DIGEST-MD5)
• Many configuration options, esp. for mail-construction.
• Full header-control, you can directly edit mail-headers before sending a message
• Stability (I hope - having used Beam for years now as my main email-client with only a few problems)
• Filter capabilities (using SIEVE and a SPAM-filter)
• Identities, separating the user-info (name, mail-address, signature) from the network-info (server-address, login & password)
• Full Support for people-files (you can create, edit and use them)
• Secure Transport (TLS, SSL), by means of OpenSSL
• Preliminary IMAP-support (fetches mails just as POP3 does)

What's going to come?

• Online user-documentation
• Virtual mail-folders, as in Postmaster
• Searching through mail-folders, with possibility to save searches as virtual folders
• Support for mailing-lists, with automatic mail-threading
• Decent IMAP support, with seamless integration into local mail-handling
• Secure mail-contents by means of GPG (Gnu Privacy Guard) and perhaps S/MIME