Emails not coming through with images shown by default

[TerencePIT]

We are shortly going to be sending phishing emails out as a test for our school. We are needing emails in Outlook web app to show the images by default rather than the user having to add to safe senders list. Going through everything I can not find a way for the life of me to get this to apply for everyone? Anyone know how to do this?

[Iain.Faulkner]

Sorry to tag onto this, I've got the same issue at one of my schools, where images don't display which is a real pain when it comes to trying to have a corporate/unified email signature for all staff.