You could also set up a Smart Campaign to trigger off of when Email Invalid is set to True.
Then, in the flow, have a Change Data Value for Email Address with the new value of "NULL". This will blank out the email address.
There are a lot of ways to do this.
I don't recommend setting the email field to NULL, but you can setup a flow that says if Email Address changes, then set Invalid=FALSE to try again.
StrikeIron is pretty good, but not 100%.
Thanks for the replies, all. Josh, what's the reason to keep an invalid email address? Perhaps the greater question would be, what are some strategies to get a user to provide a valid email address when their email address is invalid?
Why not just delete all users with blank or broken email address. Sure they can (hopefully) be cookied and fill in a form that would update their email; however, this would be the same if there was no entry and the person just filled in a form and was entered as a new user.
Please advise pro/con.