>The question that should be asked is if not using IMAP gives for this app any edge over not using it? It seems that the answer is no.
This isn't true and it seems you have never used the app, so you don't know if an IMAP implementation doesn't actually have an edge over it.
IIRC, Mailbox actually had the ability to read your emails - some of the features they provided meant their servers had to have access to your inbox. Now, for this to work on IMAP, that meant giving Mailbox your email and password, and for Mailbox to store that in more-or-less plaintext.
Now as an enduser using Gmail, would you prefer that Mailbox stored your password somewhere in us-east-1, or an easily revokable oauth token?
Mailbox only works with Gmail and iCloud Mail. Gmail supports OAuth2.0 [0] while iCloud does not [1,2]. On the other hand, Outlook supports OAuth2.0 [3] and is not supported by Mailbox.
Thus, even if the choice of the authors of Mailbox gave them some edge, it is surely not the one you described.
That, sadly, is why I am not longer an Apple user.
1990-2000, I was an enormous Apple fanatic. I went to user group meetings. I read everything I could get my hands on about their tech.
When I learned to program C/C++ on windows machines at school, I'd come home and re-implement what I had learned using Codewarrior on my Mac.
Then, Jobs's return marked an era of change for change's sake. Apple went from being "different because different is better" to being "different because different is different".
I'm all about progress and improvement but I despise unnecessary and unproductive change.
The question that should be asked is if not using IMAP gives for this app any edge over not using it? It seems that the answer is no.