[MM3-users] HyperKitty and duplicate emails across maillists

How does HyperKitty handle duplicate messages/message-ids across maillists?

We have quite a few lists that are members of other lists.

I'm in the process of importing our old Mailman 2.1 archives and seeing a lot of duplicate message errors, and wondering if this is why.

Would new messages coming into Mailman be handled the same way?

Thanks, Derek