If you can sync your email when the firewall is turned off, you'll need to allow the Mail and Calendar apps through the firewall. Windows Defender Security Center is free security software that's included with Windows 10. If you haven't installed alternative security software, you should temporarily turn off Windows Defender Security Center. Test other Outlook Login Issues Troubleshooting programs or websites to be sure Outlook is the only problem.

Method 4: Recreating the Outlook Profile

However once I joined this computer back to the domain and let it sit for a few days it was also working fine. Once the client started using Outlook again after some time has passed the issue had come back. I’ve tried to set cache mode from 1 year all the way down to a few days. If your password isn't the problem, you might have a certificate error. If so, you'll see a message that says, "There is a problem with the server's security certificate. The security certificate Outlook data file cannot be accessed is not from a trusted certifying authority."

Check the connectivity to your email server

• I’ve unchecked download shared folders when setting up a new Outlook profile.
• Below are the steps I’ve taken to try to resolve this issue.
• Firewalls and antivirus software might prevent you from syncing your email and calendar events.
• This solution will be beneficial for users who are facing Outlook syncing issues because of corrupted PST or OST files.

You'll also receive a mail (to the alternate email and to your admin email) from Microsoft Repair Outlook Profile Online 365 that indicates your tenant has encountered directory synchronization errors. For details see Identify directory synchronization errors in Microsoft 365. I still have it turned on on my laptop and it has not shown any issues yet.

Methods to fix Microsoft Outlook syncing error

To solve your Outlook issues, download the application from the Microsoft website and follow the directions. If I check the sync log I see a lot of sync errors for Inbox, sent items and a few other folders. The most common cause of an out-of-date account is an incorrect password. In the notification bar at the top of the app, select Fix account. If your password is incorrect, you'll see a message asking you to update your password.

Microsoft Outlook Sync issues

This blog talks about the causes behind Outlook synchronization errors and a few solutions to fix Outlook sync issues. We have shared five manual methods in this blog to resolve the Outlook syncing errors. Apart from this, we also discuss the Shoviv OST to PST Converter Tool, a professional way to repair, recover, and convert Outlook data files. This solution will be beneficial for users who are facing Outlook syncing issues because of corrupted PST or OST files. Users can also try its free demo version in their system and process the first 50 items from each folder freely.