Simply open the email and check the entire letter to find the product key. On the other hand, if you have purchased MS Office online, then there is a high probability that you have received a confirmation email with the product key in it. Secondly, if you purchased a CD/DVD then the product key is usually located on the back side of CD case, simply flip the CD/DVD case and the product key should be written there. In some cases, the product box may contain some label cards that contains the product key. If you have purchased MS Office from a store then there is a high chance that the product key is written on the backside of the product cover. Solution #1: Check the Product Box or E-mail to Find Office Product Key Solution #3: Recover MS Office Key Using Product Key Finder.Solution #2: Recover MS Office Product Key from Registry Entries.Solution #1: Check the Product Box or E-mail to Find Office Product Key.