Ask HN: Email list security with 3rd parties?

Wasn't sure how to word that title.

I've been working with MailChimp to handle my app's emails. I recently met someone who I otherwise like (cool guy) who offers the same service specific to my metro area. He agreed to match the price I was currently paying and I agreed to switch over. Being the paranoid person I am I immediately started thinking about security.

In my mind the danger of MailChimp selling my emails is relatively low. Even if I'm naïve about that I think the likelihood is low they would end up selling to a direct competitor of mine.

On the other hand, someone handling my emails locally would conceivably know my competitors personally. Given the value of those emails to a competitor, I was thinking the temptation to make some extra money might be too great, if not for the owner than maybe one of his staff.

Regardless, I want to move forward with them for a host of reasons. But I don't want to do so blind.

My only idea for monitoring the situation so far is to set up numerous fake emails accounts and 'poison' my list to keep an eye on it. If another local business hits those accounts I think it would be clear there was a breach.

Has anyone dealt with this? Is there another monitoring solution?

Thanks.