I have seen this happen before, most likely since you did not upgrade the site admin schema this is due to the user that you have logged into site admin having a missing email address for that user account. The test email that is sent from the site configuration tab is considered a manual email from QC so the user that is sending the email must have an email address associated with the login, this is because an email must have a ''from'' in order to be sent. If automail is sent from qc and no email address has been specified at the project level it is sent from the default ''tduser@domain.com'' but in the case of a manually triggered email (such as the test email) in QC the currently logged in user must have an email address specified on their account.

If this does not fix the issue I would take a look at the SA log file, this should give a more descriptive error as to why the test email cannot be sent.