Fixing Outlook SSL Certificate Warnings

If Outlook shows a certificate warning like "The name on the security certificate is invalid" or "The server you are connected to is using a security certificate that cannot be verified," it means the SSL certificate on the mail server doesn't match the hostname your email client is connecting to. This is easy to fix and doesn't mean your connection is insecure.

01. Why This Happens

When you connect to a mail server over SSL, your email client checks that the SSL certificate matches the hostname you're connecting to. If you connect to mail.yourdomain.com but the server's certificate is issued for web150.ultrawebhosting.com, the names don't match and your client shows a warning.

This happens because:

• The server's primary SSL certificate covers its own hostname (webXXX.ultrawebhosting.com), not every customer's domain
• Your domain may not have a valid SSL certificate yet (AutoSSL hasn't run), or the certificate expired and is pending renewal
• You're using an IP address instead of a hostname to connect

02. The Fix

1. Find your server hostname - log into your client area, click your hosting service, and note the Server Name (e.g., web150.ultrawebhosting.com)
2. Update Outlook - go to File > Account Settings > Account Settings, double-click your email account
3. Change both server names - set Incoming mail server and Outgoing mail server (SMTP) to your server hostname
4. Click More Settings > Advanced - verify ports are 993 (IMAP) or 995 (POP3) incoming, 465 outgoing, both with SSL/TLS
5. Click OK and test - the certificate warning should be gone

Alternative: Fix Your Domain's SSL Certificate

If you prefer to use mail.yourdomain.com, make sure your domain has a valid SSL certificate that covers the mail subdomain. In cPanel > SSL/TLS Status, check if mail.yourdomain.com has a valid certificate. If not, click "Run AutoSSL" to issue one. Once the certificate is active, the warning goes away.

03. After Updating the Server Name

Update the server name on all devices that use this email account (phone, tablet, other computers). The setting change needs to match everywhere.

For complete email setup instructions, see our guides for Outlook, iPhone, and Android. For other Outlook errors, see our Outlook Error Guide.

Quick Recap

1. Use your server hostname - webXXX.ultrawebhosting.com instead of mail.yourdomain.com
2. Find it in client area - under your hosting service details
3. Update both incoming and outgoing - in your email client's account settings
4. Or fix your domain's SSL - cPanel > SSL/TLS Status > Run AutoSSL
5. Update all devices - the hostname change needs to match everywhere

Last updated March 2026 · Browse all Email articles