Thunderbird, Microsoft Office Outlook, Apple Mail, Mailbird, Evolution, Mailspring, Postbox, eM Client, Microsoft Mail and Calendar, Fuser, Orbit Communicator, Falkon, Iridium Browser, Claws Mail, OpenGOO, Boxbe, Clyton, FossaMail, Unified Inbox, Nettalk, Mail Pilot, Bigstring, Threadsy, Office123 are some alternatives to Zimbra Desktop.