FalconMailer is a Java-based Mail API that can send emails quickly and efficiently. The API is easy to use and is much faster than the JavaMail. FalconMailer uses SSL.
Microsoft Exchange compatible server and client libraries
OpenChange is a portable Open Source implementation of Microsoft Exchange server and Exchange protocols. It provides a complete solution to interoperate with Microsoft Outlook clients or Microsoft Exchange servers.
OpenChange client-side library is used in existing messaging clients and is the solution in new projects to communicate natively with Microsoft Exchange and Exchange-compatible servers. OpenChange server is a transparent Microsoft Exchange server replacement using native...
Your own mailing system (most easiest to use with zero configuration) for the entire world (available in almost all the languages of the world) which will include Mail User Agent and Mail Transfer Agent thus trying to give maximum speed while transferrin
Elmo is a feature-rich console mail client for UN*X power users. It integrates functionality commonly realised by separate pieces of software in other mailers.