Outlook Mail Synchronization Issue – Multiple Users

Question

Dear Team,

We are currently facing an Outlook mail synchronization issue. Emails are not syncing properly in Outlook for approximately 4–5 users.

We have already tried the following troubleshooting steps:

1. Deleted the Outlook data file (OST) and allowed Outlook to regenerate a new file.
2. Performed Microsoft Office repair and installed the latest Office updates.
3. Removed the Microsoft credentials from Windows Credential Manager and signed in again. Web browser authentication was successful.
4. Created and configured a new Outlook profile.
5. Verified two-step verification and authentication/security settings.

However, the issue is still not resolved, and emails are not syncing in Outlook.

The important point is that the same issue is affecting multiple users, and the affected users belong to different domains. Therefore, this does not appear to be an issue specific to a single user profile, OST file, or domain.

Answer 1

Hello Airlock Team,

Thank you for outlining the troubleshooting steps you have already completed.

Since the OST files and Outlook profiles have already been recreated, and Office repair, updates, credentials, and authentication settings have been checked, I would like to gather a few additional details to help narrow down where the issue is occurring.

Could you please confirm what type of email account is configured for affected users? In Classic Outlook for Windows, please go to File > Info. Under Account Information, the account type should appear directly below the email address, for example, Microsoft Exchange, IMAP, or POP.

Also, although the users belong to different domains, please confirm whether these domains are hosted within the same Microsoft 365 tenant or managed by the same email provider.

As the next comparison, please ask the affected users to test the mailbox in both New Outlook for Windows and Outlook on the web.

To switch from Classic Outlook to New Outlook, turn on the "Try the new Outlook" toggle in the upper-right corner of the Classic Outlook window or open the Help tab in New Outlook and select "Go to classic Outlook". After New Outlook opens, please check whether the latest emails and folder changes are synchronized correctly.

Please also sign in to Outlook on the web using the same affected account: https://outlook.office.com/

Please let me know whether the missing or delayed emails appear correctly in New Outlook and Outlook on the web.

Could you also confirm the following details?

• Does Outlook display Working Offline, Disconnected, Trying to connect, or Password required?
• Are the affected users working from the same network, office location, or device configuration?

Please share the results when available. This additional information will give us a clearer picture of the issue and help determine the most appropriate next steps.

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