Frequently Asked Questions

Overview

This message appears when your iPhone cannot confirm the security certificate for Microsoft’s Outlook/Office 365 mail servers. It does not mean your mailbox is compromised - it usually indicates a temporary certificate or network validation issue.

Step 1: Restart the iPhone

Restarting clears:

• Cached SSL certificates
• DNS lookups
• Stuck background processes for Mail and Keychain

Why it works: Microsoft frequently rotates SSL certificates and server clusters. A reboot forces iOS to download a fresh, valid certificate chain.

Steps:

• Hold the power and volume button until “Slide to Power Off” appears.
• Slide to shut down.
• Wait 10 seconds, then power back on.
• Check Mail again — most issues resolve at this step.

Step 2: Switch Networks

If the warning reappears:

• Disable Wi-Fi and test on cellular (or vice versa). 
• Some Wi-Fi networks (hotels, offices, or filtered networks) may intercept SSL traffic or cache DNS records incorrectly.

Why it works: If the issue disappears on a different network, the problem is with the Wi-Fi network’s DNS or SSL inspection settings.

Step 3: Re-Verify Mail Settings

• Open Settings → Mail → Accounts → [your Outlook/Office 365 account].
• Verify your email address and server name are correct.
• Make sure the Use SSL option is enabled under Advanced.
• If you see any unrecognized hostnames or a custom domain (e.g., mail.yourdomain.com), switch it back to the standard Microsoft endpoint (outlook.office365.com).

Step 4: Delete and Re-Add the Account

• Go to Settings → Mail → Accounts.
• Tap the affected Outlook account → Delete Account.
• Restart your iPhone. Re-add the account using Add Account → Microsoft Exchange or Outlook.com.
• Sign in with your Microsoft 365 credentials.

Why it works: This refreshes all cached trust and authentication tokens.

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Optional Steps If Request by NTELogic Technicians:

• Capture a screenshot of the certificate warning.
• Check the device’s date/time settings (incorrect clock = invalid SSL).
• Verify endpoint reachability using ping outlook.office365.com from a laptop on the same network.
• Open a Microsoft 365 service ticket if the certificate chain itself is invalid or mismatched.