SM server (linux) went live last night (9546), I migrated the mailboxes overnight but started the users with blank mailboxes and have been importing today. However some of the mailboxes that had not yet received historical emails are getting new blank emails with [This message has no Text content]

I know the emails are coming in with content as a copy of the incoming emails are arriving in another mailbox due to a content filter rule, and that email displays fine, but under Outlook (MAPI) and webmail, there's not content.

It's not just one, there's several across all mailboxes, seems to be random.

Are they lost? can they be rebuilt? what can I do to prevent it?