Fixing “Certificate Name Mismatch” or “Cannot Verify Server Identity” Email Errors

Some email apps show a warning such as "certificate name mismatch" (Outlook, Thunderbird) or "Cannot Verify Server Identity" (iPhone, iPad, Mac) when you connect to your FimuroHost mailbox. It usually appears when the app is set up with a server name based on your own domain.

Why it happens

Suppose your app connects to imap.yourdomain.com or mail.yourdomain.com, and that name points to our mail servers. The secure certificate on those servers is issued for *.stackmail.com, not for your domain. Your app notices that the name it asked for is different from the name on the certificate and warns you.

The warning is expected in this setup and is not a sign of an attack: the certificate is valid and your connection is still encrypted.

Fix 1 (recommended): use the stackmail.com server names

Change the server names in your email app's account settings to:

Because the name now matches the certificate, the warning goes away for good. Keep your existing username (your full email address) and password.

Fix 2: trust the certificate

If you'd rather keep your current server names, you can accept the certificate when prompted. First check that the certificate details show *.stackmail.com. If it shows something else, don't accept it — contact us instead.

• iPhone / iPad: tap Details, check the name, then tap Trust.
• Outlook: choose View Certificate to check it, then Yes to continue.
• Thunderbird: confirm the security exception after reviewing the certificate.

Once trusted, the warning shouldn't return unless the certificate is renewed or replaced — at which point you may see it again. That's why Fix 1 is the better long-term choice.

Need help?

If something doesn't work as described, our team is happy to take a look. Open a support ticket or message us on WhatsApp at 01818160926.