Mail notifications on the action center is all good but some users like it the way it was grouped by account in Windows Phone 8.1. Thankfully, windows 10 now has an option to group it or to leave it under a single group.
- Launch the mail.
- Tap on the ellipsis to open the action menu.
- Tap on Settings.
- Tap on Notifications.
- Turn on “Group notifications by account in action center”
- You will get a warning that the current pinned tiles for mails will be removed and created again by account.
- Tap Ok to continue
- Check “Apply to all accounts”.