I think it was just a promotional email. The reason they found out where your husband lives is most likely because YOU clicked on the ad. When you clicked on the ad it fired what is called a tracking pixel. In layman's terms this is technology used by email marketers. Anytime someone clicks on one of the images in the email is will send a report to the person sending the message. These reports can range anywhere from the geo-location, the IP address, the state, the browser (Mozilla Firefox, Internet Explorer) used when clicking on the image and a few other metrics can be recorded as well.
This is fairly common amongst big data marketers. It's a simple marketing tactic. Once you click on the image in the email you will be redirected to a page in your browser with info such as your geo-location (your zip code in this case) then the person that the ad was meant for will show interest in the product because it promises/advertises they will find singles in that specific city. It's called "targeted-marketing" the more targeted it is (the more info they have on the person like the location, their preference of singles as in Males, or Females, their age, etc) the more likely it is that the person viewing the ad will find it more enticing and will likely sign up for the offer.
So I really think it was a promo email. But like i said you won't really know how that email marketer got the email in the first place. He could have registered on to a different dating site and the marketing division of that dating site used their current customers to promote other related products (in this case Match.com because anyone that registered for the dating site has shown interest in online dating so its more likely these emails will work in driving more sign ups/sales)
Your only other choice is to monitor his email activity and keep an eye out for the emails I told you about. Promo emails and transactional emails (a quick google of these terms might do a better job at explaining the difference) and in the meantime give him the benefit of the doubt.