beam is described as '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' and is an app in the Office & Productivity category. There are four alternatives to beam for a variety of platforms, including Linux, Windows, BSD, Mac and Online / Web-based. The best alternative is Claws Mail, which is both free and Open Source. Other great apps like beam are Sylpheed (Free, Open Source), Nextcloud Mail (Free, Open Source) and i.Scribe (InScribe) (Freemium).
Claws Mail is an email client (and news reader), based on GTK+, featuring Quick response Graceful, and sophisticated interface Easy configuration, intuitive operation Abundant features Extensibility Robustness and stability
InScribe is a small and fast email client with an intergrated contact database and calendar. InScribe is the PRO version with UNLIMITED Receive Accounts and Email Identities i.Scribe is free version ... with limitations.