Check down detector https://downdetector.com/
to see if there are any problems with your email providers, if not follow below.
1. Re-start the computer
2. Make sure you have a solid internet connection
3. Make sure you have all the latest updates (Including those for the Office Program)
4. Make sure your anti-virus is up to date (If you are using the Windows Defender make sure it has updated)
5. Check to see if anything else is not working (If it relates to the network run the network troubleshooter)
6. Run Office Repair
If the above fails then it possible that your profile is corrupted, go here and follow the instructions here
Hopefully you can soon get back up and running.
NOTE: As Graham says you can temporally use the Email providers web service to check you email while you are getting things sorted.