That red "X" means that the file for that photo is missing or not accessible.
This usualy means an external file NOT included in the e-mail itself.
The probable causes are (from more to tess probable):
Almost all e-mail providers, like hotmail, do block all images from senders not on your contacts list. They also block image from any un-approved sender, even those from your contacts list.
- In this case, there is a note before the message that tells you it's the case. You can allow the images in this case or set a rule to always load images from that sender.
The sender sent you a link to a file on his computer using a local address like: C:\my images\image.jpg
That file is not present on your computer and can't be displayed.
- Ask the sender to send you the actual file and not it's address on his computer.
It's a link to some image hosting site. The image is no longer stored there OR you need a user name and password to access it.
- Ask the sender to send you the actual file or give you a link that don't need you to log in to access.
It's a "hard link" or "deep link" to some image hosted on some tierse party web page. Most sites don't allow that and will block that kind of access.
- Ask for a link to the page where the image is located.
Electro, October 2011