Can't send email to registered users

I see that some security was added so that emails don't get sent to people that shouldn't get emails. I had fixed this by using a pre-send script that filtered out email addresses. However now with the new change, emails are not getting sent at all. I use the unix database backend for my Jenkins system. If I goto the People page I see 2 entries for myself, one as "Jon Schewe" with an email address "jon@domain1.com". I see a second one as "user1" (which is my unix username) with email address "jon@domain2.com". If I setup a job to send email to "jon@domain1.com" I get the error that the email will not be sent to unregistered users. If I send an email to "jon@domain2.com", then it works. Note that I've set "domain2.com" as my default email suffix.

So the first question here is what is a registered user when using the unix database backend?

Second, what is considered the email address for a registered user when using the unix database backend?