@TomaszuPL: Please can you try opening the Email app > Tap the 3 lines in the top left > Tap the cog in the top right of the pop up window > Select your account > Sync account, and toggle this option off. It's a bit of a workaround, but you can then toggle the option on when you want to manually sync your emails, and this should prevent any unwanted syncs. Alternatively, set Sync Account to 'On' and check the following:
1) Email Sync Schedule > Set Sync Schedule > Manual
2) Sync Schedule While Roaming > Manually
3) Peak Schedule > Sync emails during peak period > Manual > Peak days > Select as appropriate. Alternatively, toggle off the Peak Schedule altogether, if you intend to manually sync your emails at all times.
Let me know if this helps.
