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 modern authentication troubleshooting 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 FixTechGuide mailbox repair steps mode to only cache 1 year.

Check the connectivity to your email server

• We have resources to help you identify potential issues and fix them.
• The Support and Recovery Assistant, a tool provided by Microsoft, can identify and resolve common Outlook problems.
• Before you begin, make sure that your device has the latest operating system and app updates.
• 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.
• If so, you'll see a message that says, "There is a problem with the server's security certificate. The security certificate is not from a trusted certifying authority."
• This solution will be beneficial for users who are facing Outlook syncing issues because of corrupted PST or OST files.

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 solve Office 365 mailbox sync delays we know the solutions, we will understand a few common causes of the Outlook sync problem.

Methods to fix Microsoft Outlook syncing error

If the connection is poor, consider restarting your modem/router or moving to a more reliable network. After these instructions, ensure the sync settings are correct and check everything is working well. I’m at wits end and Microsoft stopped helping me because they feel the problem is on our end. However, I cannot find any reason why his account would do this only on our domain nothing is blocking our connection to Office 365. 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.

Microsoft Outlook Sync issues

I’ve tried the Microsoft office uninstall tool provided by Microsoft (which deletes more items then just control panel uninstall). Below are the steps I’ve taken to try to resolve this issue. Two-factor authentication helps protect your account by making it more difficult for someone else to sign in. It verifies your identity using your password and a contact method (also known as security info). Outlook will show as connected to Exchange but is not receiving any new email. This can happen for days at a time, and then disappear for a day or 2, only to appear again.