After you do a job, you need to decide that day whether or not you want to mail to them.
If they are moving out or it's a rental of another owner...get their new or main address (if in your area) and ad that as the primary site.
If they are moving out of the area or you just don't want to "remind" them....click the "do not mail" box on their profile page.
When I get return mail, I make it a point to fix it in the profiles of the returned mails inteneded recipients.
I don't want to have to waste another buck 25 on nuthin...... a second time.