yeah, about that... the best thing i have managed to achieve is to get good battery life for a few days. Then the drain inevitably comes back on its own. I thought all this was mail related, but it seems that it is not.
The thing is that i can get a good battery life (3% drop per night), use it for 2 days with a single charge but then the drain would come back randomly and stay. I really don't know the cause for that. For example, i had the good battery life, went to sleep, during the night the phone lost 3% (which is brilliant), the i watched youtube, browsed my photos for an hour and then put my phone away (all apps closed). the phone remained idle but now it was draining again. This leads me to think that somehow in the morning i did something that triggered a background process that began to drain the battery. But now i know that this specific occasion is not mail related as i uninstalled mail a week ago or so. The only apps i opened were settings, youtube, snapchat and photos; and after that the drain started again.
Food for thoughts.
Another thing is that i was doing force restart very often, and my battery was starting to act funny (uneven discharge with big drops, even increase in battery level with no charger connected) but i fixed this by doing a power cycle (discharging to 15% or so, then connecting a charger, turning off my phone, charging for 3 hours or so, then turning my phone on and doing a force restart) - also an interesting thing is that after this procedure the drain went away for a few days as well.
Food for thoughts again.