hMail Server, Microsoft Exchange Server, Zimbra Collaboration Suite, mailcow: dockerized, mail.com, Mail-in-a-box, Emails, Modoboa, Mailu, AOL Mail, OBM, nPOPuk, MyInfo, Poste.io, DBMail, Fuser, Pegasus Mail, Calypso, OpenChange, Mercury Mail Transport System, WildDuck, UKs Kalender, NOCC, OpenGOO, Zarafa, Windows Contacts, Boxbe, iCalViewer, Expanding Communication, Collabair Team Collaboration Suite, phlyMail, Sqwiggle, HipCal, 1calendar, Inbox Cat, Bigstring, HyperOffice Email Service, Omea Pro, Threadsy are some alternatives to IRedMail.