I'm using dataloader to import EmailMessages from an existing org to a new one. Everything works fine except that I cannot set the "CreatedById"/"CreatedDate" fields despite the fact that I have audit field settings enabled correctly.
I can set this field on basically every other object but it doesn't seem available for the EmailMessage records. This is a problem because the chatter feed shows the wrong user/date and it's important information for case support users.

Does anybody know how you can import EmailMessage records with the CreatedBy user intact from the source?

Thanks,
Jimmy