Have setup email app with an Exchange account linked to Office 365. The initial setup does load mails and syncs the calendar but after that no mails are sent or received. Hav tried with smart push , normal push, delayed every 5 minutes. not results. Manually syncing does not work and sometimes no connection warning comes up even though connection is up.

This "problem" isn't related to our devices, is related to Google's silly things about Android (what a surprise!).

I'll try to help you, anyway.
This link should contain some useful infos and solutions, focus on the comments.
https://www.thurrott.com/mobile/android ... t-accounts

By the way, i use my BV8000 pro with my microsoft account (Exchange) without any issue.