Tiki and ((Cypht)) webmail interoperability started with ((Tiki20)). Major work has been done since that time in Cypht, and in Tiki 21, 22, 23, 24, 25 and 26. Work is ongoing, so it's recommended to run the latest 26.x (and 27.x when released) from Git or ((dev:Daily Build)). Most enhancements and many fixes will not be backported as there are lots of changes. Please see this [https://dev.tiki.org/item8365-Race-condition-Sessions-stored-in-the-database-and-Cypht|known issue].