Photo's in an email have changed to small grey boxes

I received an email with about 10 pics in it. I replied "Thank you". Then when I wanted to see the photos again they are all small grey boxes and I cant see them anymore.

This is infuriating, what the hell has happened to them. I have to get the sender to resend them now. Crazy !

Some mail providers block images from 'suspicious' senders before the message is downloaded, so it sometimes works to access the account through webmail and allow remote content from the sender or add it to the contacts listed in the webmail controls.