Email content blocked

I have a MacBook Pro and suddenly my emails show "Your network preferences prevent content from loading privately" and I have to use "Load Content Directly" for each and every email to read them. This just started. What do I do to go back to being able to read my emails?? I am nmot that computer literate buy did try to go to mail and then preferences, but when i go to the mail tab there is no Preferences tab??