I used a client's email address when I was setting up some accounts for him as a test run. I've since taken over the account and set up a few other blogs and now have to transfer ownership of one of the blogs elsewhere. I just can't tell where the email address was used. I've checked each active account that I can think of and can't find it, therefore the client can't use the email address to set up his new blog. How can I find out where the email address was used?
The blog I need help with is sanctifiedbrother.wordpress.com.