The Problem: Outlook 2007 "The server you are connecting to is using a security certificate that cannot be verified. The target principal name is incorrect"
If you use Yahoo sbcglobal.net, here is the fix:
You probably had outlook 2007 configure the settings for you.
The fix: Go to Tools>Account Settings>
Choose the sbcglobal.net account
Click "Change"
Change the incoming mail server from "pop.sbcglobal.yahoo.com" to "pop.mail.yahoo.com"
For outgoing server put smtp.mail.yahoo.com
click finish.
This should take care of it.
If you have AOL and had outlook configure it for you then you probably have the same problem, just go to aol site and find the correct incoming and outgoing mail server and change the settings in outlook.
I use sbcglobal.net