How can I get Outlook to accept 'safe senders'?

I have Microsoft Office Outlook 2007. I have quite a few daily emails that I get, and for some reason it will never download the pictures automatically. I have tried adding the sender, the sender’s domain, everything I can think of, but still Outlook nobly protects me from pictures… I know this is not right up there on the list of life’s problems, but still- anybody know what I can do to convince it that I’d really rather not have to go through telling it I want the pictures every single time??