That notice is informational ONLY.
That is NOT what is keeping the mail from displaying.
Do you also see a button (Load Remote Content) ??
That button says the additional information has been deliberately suppressed by your anti-SPAM settings in Mail. The additional information would be supplied (via Links) from the Sender's Server, but your settings have suppressed BOTH:
• the loading of the boilerplate information or pictures from the Email Sender's server.
• Ratting you out to SPAMMERS as a 'live' email address.