We have just integrated our Global Opt Out (GOO) functionality. What this will do is add any opt outs in you account to an opt-out list that is recognised by all of the lists in your account. It can be switched off which means opt-outs are processed for the list only or on which means that the user will be opted-out of all lists on your system. Numbers can also be imported to the list so if you have a suppression list that you would like recognised by our system you can just switch on the GOO system, upload them to the list and they will be permanently suppressed by your account.
The system is on by default on all new accounts and off by default on all existing accounts.