Gemini Mail   
http://www.intellegit.com

Gemini is an advanced multi-platform, standards compliant, messaging client with powerful features for managing mail from multiple sources. Gemini provides flexible filtering of messages and protection from junk mail, viruses and common breaches of netiquette, in an attractive interface which is easy to use yet hides nothing from the more advanced user. Additional features include message templates, auto-replies, support for multiple identities, HTML, IMAP, SSL, editing of stored messages, spell checking, syntax colouring and encryption/signing via integration with GnuPG.