Microsoft Outlook - Internet Security Warning - The target principal name is incorrect


EQ Forum Admin
Staff member
Did you get the following error message from Microsoft Outlook?

Internet Security Warning - The server you are connected to is using a security certificate that cannot be verified

Microsoft Outlook Internet Security Warning.jpg

The most common reason for "The target principle name is incorrect" is due to the way many ISP's and hosting companies branded the email settings for their customers. Often in the past email services would create in DNS and then tell customers to use names such as imap pop3 and instead of imap pop3 or As these customers update their settings to use SSL enabled ports switching pop3 from 110 to 995 and imap from 143 to 993 they're getting an error because the name on the certificate is the email service providers name and not their own. The fix is for these customers to use to the email services email settings such as instead of the branded settings using the names from within their own domain name.

It's also possible the error was caused by the email service provider updating to a new company name on the same IP address instead of using a new IP address for the new server names.