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 and 25. Work is ongoing, so it's recommended to run the latest 25.x (and 26.x when released) from Git or ((dev:Daily Build)). Most enhancements and many fixes will not be backported as there are lots of changes.