Currently Being ModeratedJul 3, 2013 12:08 AM (in response to MEBerry)
If you haven't already, try re-installing the update using the combo installer:
Although you're unlikely to need it, make sure you have backup of your data just in case.
Currently Being ModeratedJul 3, 2013 12:20 AM (in response to MEBerry)
Many times this occurs because you may have previously moved the Mail application out of the Applications folder and are still accessing Mail via its Dock icon.
Try looking in your Applications folder and starting Mail from that location. If a 2nd Mail icon apperas in your Dock, then that was the issue.
If the Mail application is not in the Applications folder, it won't be updated to a newer version. It will be orphaned and the newer version will be installed in the Applications folder.