Boomerang

Now this app will power through your emails and let you breathe again. You can ‘snooze’ emails to come back later (boomerang) when you have time to deal with them. Schedule emails to be sent at a later date or time, meaning your emails sent last thing at night can be in their inbox at a godlier hour. This is great for sending a press release to hit the reporters desk at the right time to hit the press run. You can track responses to your emails too. If you don’t get a response, then the app will remind you. The personal favourite is the ability to pause your inbox! Yes, stop receiving email while you complete a focused task. There are lots more features in the premium package, including an assistant that uses AI to help you write better.

Currently integrates with Gmail, Google Apps, and Microsoft Exchange accounts, though they are looking to include others in the future. So you can put it as an add-in on your Outlook 16 Office 365.