When your colleague leaves his/her desk, open Word, go to Tools, then Autocorrect Options and then select “AutoCorrect”.

Add some stuff to the 'Replace' and 'With' boxes. For example, replace:

=> 'Dear' with 'Yo Baby !' or 'My darling'
=> 'Thank you' with 'Cheers mate'
=> 'Email' with something completely irrelevant, like 'pizza'
=> colleague's name with 'Miserable Rat’ in case of male colleague or 'Old spanker' in case of a female

To make sure that they use Word for emails. Quickly go to Microsoft Outlook, go to Tools, Options, Mail Format and tick the 'use Word' check box.

That's it...now you are all set !
Wait till your colleague sends out an email to your boss