Initially, the proposition relied on Fastmail protocol, which was/is superior to IMAP.
It was pleasing that standardization began, as MS Activesync charged a few dollars per user just for the protocol.
Even the Apache James mail server supported it as a draft.
Despite becoming a standard make it better , but lost momentum.
Still hope at least both will add push notification to 3th party apps.
And a BIG hope for https://stalw.art/
