With such a large number of connection issues with Outlook 2016 connecting to Office 365 you would think someone would have the definitive answer to these persistent issues. It is unfortunate that the issues that plague Outlook 2016 are not all related. Hopefully after you have read this technical note you too will be able to resolve your issue. Although this is not the fix that will fix all Outlook connectivity issues, but then again it might fix yours.
I guess starting with the obvious is always a good place to begin.
- Is there an Internet connection that works?
- Can you connect to the mail server via the web browser and login to your mail account?
- Does Outlook provide any helpful error message about the connection failure?
- Can you resolve the domain name to a valid IP address using the command NSLOOKUP?
These might seem obvious but with each of these test above indicating no problem there may still be an issue with the Internet. After spending two hours at a client working on her Outlook 2016 connectivity issue performing each of these tests, they all had positive results except the last. However, after flushing the DNS cache I was able to get the last option to provide a favorable response. So what was next?
I try to leave any destructive action for last. So backing up the mailbox, wiping out the Outlook profile, and recreating her Outlook profile was my last resort. It was in the recreation process of the Outlook profile that I found the router was not working correctly even though it gave every indication that there was nothing wrong. Outlook 2016, which is known for issues resolving the mail server in the autodiscover process, would not complete the setup. After rebooting the Comcast router and waiting about 15 minutes for it to become ready for use, Outlook finally made the connection and completed the auto configuration.
As I noted earlier, this might not be the solution you need. You may have to troubleshoot this deeper. Here are some additional Microsoft technotes that may help.
We hope that this information is helpful. Please let us know how this has helped you or if you have additional questions. As always Firestone Technical Resources, Inc. is here to help with your computer support issues - "Providing personal service for your impersonal technology."