Fastmail.
Can you choose which folders use real-time push vs which folders use polling?
I’m afraid not. I’m pretty sure the entire account uses polling. I’ll usually open the app and hit F5 to quickly poll for results, otherwise I’m waiting for the next sync.
Having said that, the unread counter works fine for sub-folders:
Edit: I was wrong, Mailspring uses the IMAP IDLE extension to wait for new mail delivery. Still doesn’t stop me from spamming F5 when I’m waiting for new mail to arrive.
Aah, now I understand.
There is no such setting that I’m immediately aware of - but I am automatically getting messages for my folders. So I’m assuming it’s doing something in the background: most likely a periodic sync for the entire account.
Definitely doesn’t sound like the behavior you wanted, my bad. But, at least there are notifications on the folders once mail is received. 😅
Edit: In the repo for their sync engine it explains:
So the foreground worker only idles on the primary folder, but it does slowly iterate over all folders in the background.
No settings have been added for this functionality (that I’m aware of).
Edit 2: Went back and read your original comment; hadn’t noticed the PR was yours. If that’s the case then you’re probably aware of how the sync works anyway. My bad if I’ve posted stuff you’re already aware of.