Inbox works through push notifications so won't be the problem.Do you have it to fetch like every 5 mins?
Decrease the sync time to 30 mins.
Potential that inbox is doing it?
On cloudmagic and my battery is perfect, 5 accounts all set up. Including Exchange Push and fetch for all pop/imap.
It's the kernel and OS that's draining the battery. Every battery app is pointing to those. I have f**k all wakelocks though and it's near on impossible to tell what else could be causing it.
I tried this morning without AK Kernel and it was just as bad. Even worse tbh but the battery drain stats still pointed to the same things