Hi Michael
As Barry suggested, there could be a problem with your Internet connection. So you can check that.
But also there can be more reasons for your error like:
1. Internet connection: If your internet connection is slow or not working properly, you need to check it.
2. Outlook Profile: In any case if your profile has been damaged, create a new profile.
3. Anti- Virus: The firewall settings most of the time prevent user to access an application generating errors.
4. Outlook Account Settings: Check your settings that all fields have been filled up properly.
5. Open Outlook in safe mode and check.
6. Clean-up e-mails, messages that might have been stuck.
Thus you can refer to the article below to solve your issue
https://support.microsoft.com/en-us/kb/813514
Thanks & Regards
Henry