Progress update:
Just got it to "work" a couple of hours ago.
- The overall approach I came up with -- really works.
- "Cloud assisted": let's make a new term to cleanly differentiate from TypeMail, MyMail etc.
- Uses GCM + my own cloud servers, but has none of the (perhaps expected) bad effects on privacy
- My cloud servers know nothing:
not the password, not the user's email address, not even the mail server hosting the account
and do not have the technical capability to access the user's emails or log into the user's account
in the unlikely event that these cloud servers get hacked, there is literally nothing there, not even the users' email addresses.
- Testing in Doze Mode looks good so far
- Looks good on Android M/6, should be good on the upcoming N (7?)
- Very low traffic and battery use
- Supports multiple folders with push per account (just like IMAP does now)
- Will be Pro version only (server expenses)
Now I've put "work" above in quotes:
Needs work (sans quotes) on error handling / failure recovery / performance testing / what if the cloud server goes down / what if GCM is unreachable... and a dozen things that I haven't yet thought of.
Cautiously optimistic for a forum-grade development build in a week, maybe, hopefully.