Outlook client prompts' Outlook 2016 upgrade in progress' when using it. The client cannot send and receive emails normally. Find the cause and solution

Question

The Outlook 2016 client is unable to send and receive emails, prompting "Upgrade is in progress, mailbox is being optimized as part of Outlook 2016 upgrade, this one-time process may take more than 15 minutes, which may affect performance during optimization", and cannot be successfully upgraded, causing mailbox to be unusable. Multiple users in the company are experiencing this situation. What causes it and how to solve it

Answer 1

Hi @森 树 ,

According to my research, the problem appears to be a known issue, you can refer to the Can't send or receive email in Outlook and "Metered Connection Warning" is triggered.

If the issue continues, here are some other steps you can take to resolve this issue:

1. Create a new profile by going to Control Panel > Mail > Show Profiles > Add**.** Set the new profile as the default and check if the issue persists.
2. Repair Office Installation: Go to Control Panel > Programs and Features, select Microsoft Office, and choose Change > Repair. This can fix any corrupted files that might be causing the issue
3. Use the Microsoft Support and Recovery Assistant (SaRA): This tool can automatically diagnose and fix many Outlook issues. You can download it from the Microsoft website and follow the instructions to run it.

Besides, if your organization is currently using Office 2016 or Office 2019, it's important to plan for upgrading to Microsoft 365 Apps before October 14, 2025, when these versions reach their end of support. Upgrading ensures that your users have access to the latest features, security updates, and can connect to Microsoft 365 services without issues.

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