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. 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)