Fix Microsoft 365 Server Not Found and Expired Certificate Errors on iPhone
Question details
Users are experiencing 'Server Not Found' or 'Expired Certificate' errors when using Outlook for iPhone and iPad connected to Microsoft 365.
- Product
- Outlook for iOS
- Device & OS
- iOS / iPadOS
- Scenario
- Attempting to connect to an Exchange or Microsoft 365 account via the Outlook app on an Apple mobile device.
- Observed behavior
- The app displays a 'Microsoft 365 server cannot be found' or 'certificate has expired' error message, preventing email access and synchronization.
Verify that your iPhone has an active internet connection and check if there are any pending iOS or Outlook app updates in the App Store before proceeding.
Gather Diagnostic Information for Administrator Support
Collect the necessary device and account details to provide to your IT administrator or Microsoft Support for a backend investigation.
Certificate and server errors are often managed at the organizational level. Collecting accurate details helps IT admins pinpoint the issue quickly.
Take a screenshot of the exact 'Server Not Found' or 'Expired Certificate' error message displayed in your Outlook app.
Note down your current iOS version from Settings > General > About, and check your Outlook app version within its settings menu.
Verify if your device is managed by Microsoft Intune or another Mobile Device Management (MDM) profile by going to Settings > General > VPN & Device Management.
Send the screenshot, software versions, subscription type, and MDM status to your IT administrator for further investigation.
Re-add Your Microsoft 365 Account
Removing and re-adding your account can sometimes refresh the server connection and fetch updated certificate configurations.
Need a Reliable Office Suite? Try WPS Office
While resolving your Microsoft 365 server issues, consider using WPS Office for your document needs. It is a lightweight, powerful, and free alternative that seamlessly handles all your Word, Excel, and PowerPoint files without relying on complex server connections.
- 1. Download and Install: Get WPS Office for free from the App Store or official website.
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- 3. Edit and Save: Make your edits and save documents locally or to your preferred cloud storage.
Frequently Asked Questions
Why does Outlook on iOS say my Microsoft 365 certificate is expired?
This error typically occurs if the SSL certificate on your organization's Exchange server has actually lapsed, or if an incorrect certificate is being cached by your network or device management software.
Can I bypass the expired certificate warning in Outlook for iOS?
No. For security purposes, Apple's iOS and the Outlook app enforce strict validation of server certificates. You cannot manually bypass this warning; the certificate must be updated by the server administrator.
How does an MDM like Intune cause Microsoft 365 connection errors?
Mobile Device Management (MDM) solutions enforce corporate security policies. If your device falls out of compliance or if the MDM pushes an outdated configuration profile, it can block Outlook from connecting to the server, resulting in 'Server Not Found' errors.
