This is only the beginning of the challenges. It only looks for .com so if you have any other top level domain this will miss it. Also using antiquated join syntax and mixing system catalog view with informationschema views is a bit odd.

I would suggest to the OP that a better solution to updating all the email addresses in your database and hoping you don't miss some would be use something like Papercut so you can intercept ANY email sent to ANY address from a given machine. It is super flexible and allows for all sorts of exceptions and detailed rules. There are other options out there of course but papercut is one I have used for this exact type of thing. It eliminates the accidental emails to customers/clients from a QA or dev machine much more accurately than updating a bunch of tables and hoping you didn't miss any.