Cannot Verify Server Identity on iPhone: What It Means and How to Fix It

If you see a “Cannot Verify Server Identity” warning when you open the Mail app on an iPhone or iPad, your device could not verify the SSL/TLS certificate of the email server it is trying to connect to. The warning usually reads “The identity of … cannot be verified by Mail” and offers Cancel, Details and Continue. In this article we explain what the error means, why it appears and how to fix it safely.

What Does “Cannot Verify Server Identity” Mean?

When an email app opens an encrypted connection to the incoming (IMAP/POP3) and outgoing (SMTP) servers, it expects the server to present an SSL certificate. The device checks three things: that the certificate is signed by a trusted certificate authority, that it has not expired, and that it matches the server name you are connecting to. If any of these fail, iOS does not automatically treat the connection as secure and shows the “cannot verify server identity” warning. In other words, the error does not mean your email account is broken; it means the security of the connection could not be verified.

Causes of the Error

• The server name does not match the certificate: The most common cause. For example, the account uses mail.yourdomain.com as the incoming server, but the server presents a certificate issued to the hosting company’s general host name (for example server123.hostingcompany.com).
• The certificate has expired: Certificates that are not renewed automatically trigger this warning once they expire.
• A self-signed certificate: iOS cannot verify certificates that were not signed by a trusted authority.
• Wrong date and time on the device: If the clock is wrong, even a valid certificate can look “not yet valid” or “expired”.
• Network interference: Login pages on public Wi-Fi networks in hotels or cafes, or security devices that inspect traffic, can replace the certificate.
• An old iOS version: Outdated systems may not recognize some certificate chains.

Is It Safe to Tap “Continue”?

You can tap Details in the warning to see who the certificate belongs to, then allow the connection with Trust or Continue. Only do this if you are sure the certificate belongs to your email provider or hosting company and you are on a network you trust. Trusting an unknown certificate on an unfamiliar network risks someone in the middle reading your email password and messages. The permanent, safe fix is to remove the cause with the steps below.

How to Fix “Cannot Verify Server Identity” on iPhone

1. Set the Date and Time Automatically

Go to Settings > General > Date & Time and turn on Set Automatically.

2. Check the Certificate Details

On the Details screen of the warning, check which domain the certificate was issued for and when it expires. If the certificate belongs to a different server name, the problem is most likely the server name in your account settings.

3. Correct the Incoming and Outgoing Server Names

Open the account under Settings > Mail > Accounts and replace the incoming and outgoing server names with the SSL-enabled server names recommended by your email provider or hosting company. This name must match the name on the certificate. Check the ports too: secure IMAP usually uses 993, POP3 uses 995, and SMTP uses 465 (SSL) or 587 (STARTTLS). For other connection problems with account settings, see our article on the cannot connect to IMAP server error.

4. Remove and Re-add the Account

If the warning continues after you correct the settings, remove the account from the device and add it again with the correct server details. Before removing it, make sure you have backed up any messages that are not kept on the server (downloaded with POP3).

5. Update iOS and Try Another Network

Update the device under Settings > General > Software Update. If the warning only appears on a particular Wi-Fi network, try mobile data; if the problem disappears, that network is the source.

Fixes for Domain and Hosting Owners

If your employees or customers who use email addresses on your own domain see this warning, the problem is most likely on the server side:

• Install a valid SSL certificate for email subdomains such as mail.yourdomain.com. AutoSSL in cPanel and the Let’s Encrypt extension in Plesk can do this for free.
• Make sure certificates renew automatically. We explain how to set up automatic renewal in cPanel in our article on automatically renewing an SSL certificate in cPanel.
• Tell users clearly which server name the certificate covers. On some servers the correct name is the server’s own host name rather than your domain.
• Use an SSL test tool to check that the certificate chain, including intermediate certificates, is installed completely.

Conclusion

The “Cannot Verify Server Identity” warning means the iPhone could not verify the email server’s certificate. In most cases, entering the correct server name, fixing the date and time or renewing an expired certificate solves the problem. If you are not sure who the certificate belongs to, ask your provider for the correct settings instead of tapping “Continue”.