GNUMail

GNUMail is a free and open-source, cross-platform e-mail client based on GNUstep and Cocoa. It is the official mail client of GNUstep and is also used in Étoilé. It was inspired by NeXTMail (NeXT's Mail.app), the predecessor of Apple Mail. GNUMail is based on the mail handling framework Pantomime. GNUMail demonstrated that it is possible to develop cross platform programs for GNUstep and Cocoa.