If I enter a never used email address in the TO field in outlook it does some kind of validation I suspect then puts an underline under the email address if it's good. If it's bad I get a dialog box that says Check Names - Microsoft Outlook does not recognize "email address" - I then have the ability to Show More Names.
The problem is it takes FOREVER to pop up that dialog box or tell me its a bad address. I'm wondering what the process is that Outlook/Exchange server uses to check these email addresses. It started doing this about 4 months ago so my hunch is something was done on the exchange server to cause this.