If I double click on the piece of mail, it will open, but in a separate window!
I had this happen just last week. Never got anything to display and decided to just dump the Windows-using sender's 'message'.
When this happens, is there a "Load remote content" button in the message Preview or window?
What do you have set in Mail->Prefs->Viewing?
How about Mail->Prefs->General?
Lastly, Mail->Prefs->Junk?
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