It Outlook 2007 and possibly previous versions a single contact entry can be displayed three different ways in the To: field: 'John Doe', John Doe and 'john.doe@example.com'.

I double checked the contact entry and there aren't any single quotes in the display name, file as, or email address fields.

This causes a big problems when I sort my Sent Items by the To: column. B/c of this undocumented feature, emails sent to a single person will end up being three different groups.

I have opened a case with Microsoft hoping that they will provide me with an answer however they are as puzzled as I am.

Any help on this issue is appreciated.