Lotus Notes images in HTML e-mail

We use Lotus Notes as an e-mail client. Recently, we sent out our company newsletter, which is an HTML e-mail with bullets, images, etc. Most of the users saw the e-mail as it should look. A few users got the e-mail, but the images were not appearing. Also, the bullets did not look the same. I've searched through preferences but cannot find anything that would prohibit images from showing in an e-mail. Anyone know where this option is?