I used to run an exchange4linux server as well as another open-source variant before that (but forgot the name... This must have been 20 years ago). The biggest

I used to run an exchange4linux server as well as another open-source variant before that (but forgot the name... This must have been 20 years ago). The biggest issue was always the Outlook plugin that had to be used, so if Grommunio has really managed to do the communication with the server natively, this seems like a big win.