Apple Mail and Drag&Drop

I have been trying to accept drops from Apple Mail which do supply data with type identifiers : com.apple.mail.email

The problem is that even though the drop says it does contain items for com.apple.mail.email it does provide the items for com.apple.mail.email.

Mail dropped from Microsoft Outlook however confirms to the protocols and returns the items for com.apple.mail.email

Is this a known issue with Apple Mail and is there are reason for what seems to be a non-compliance to it own standards in Apple Mail?

Apple Mail and Drag&Drop
 
 
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