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 clear Outlook credentials manager programs or websites to be sure Outlook is the only problem.

Method 4: Recreating the Outlook Profile

Another which is shown below, is a user opens a new message, or replies to one, and lets it sit for a while. When they go back to the message and press send they get an error that the message has been deleted. Ive repaired the OST and changed cache Exchange connectivity diagnostic mode to only cache 1 year.

Check the connectivity to your email server

• This software also has a splitter option to split large-sized PST files into smaller ones, helping users prevent oversized PST file issues.
• You'll also receive a mail (to the alternate email and to your admin email) from Microsoft 365 that indicates your tenant has encountered directory synchronization errors.
• It is possible for a corrupted Outlook profile to impede synchronization.
• If you're using an Outlook.com, Microsoft 365, or Exchange account, you won't have advanced mailbox settings unless the account was set up using advanced setup.
• I’m at wits end and Microsoft stopped helping me because they feel the problem is on our end.
• Here is the strange part I tried to remove the computer from the domain and have Outlook run from a local account for a few days.

After performing these steps, Outlook’s all folders will be synced to the server. If this method doesn’t work for you, navigate to other solutions. There can be several reasons for the Outlook synchronization error. Before credential loop in Microsoft 365 we know the solutions, we will understand a few common causes of the Outlook sync problem.

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 The most common cause of an out-of-date account is an incorrect password.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

To make sure there are no issues, click Test Account Settings to test the connection. It is possible for a corrupted Outlook profile to impede synchronization. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. If the problems do not occur in safe mode, its most likely an add-in causing grief. I’ve been in contact with Microsoft they had me migrate his account\data to another server this did not fix it.