I doubt you need offshore hosting if you're truly running an opt-in list. We have a mailing list service for our clients and send 100,000+ emails a day through many different mail servers in many different datacenters, receive many unsubscribe requests, spam complaints, etc... and as long as they are acted on, nothing is ever risked.
It all depends on how you run your list, and how you respond that makes the difference. If you're not actually sending spam or UCE, and take care of issues as they arise, I would say most DC's would not have a problem with your list.
- John C.