When you get a standard Moodle forum email in Outlook 2003 it blocks the image of the sender and replaces it with a box with the following text:
"Right-click here to download pictures. To help protect your privacy Outlook prevented automatic download of this picture from the internet. Picture of Joe Bloggs"
The last sentence is the alt text of the image.
This big long sentence pushes the actual text of the email away to the right-hand side and it reads down in a tiny little column. Screenshot attached, note that the text was actually of the screen before I resized the two left columns.
This can be fixed by adding appropriate height and width tags to the image (or perhaps rewriting the forum post/email formatting so it's not a table)
Similar, though not quite as bad happens with Gmail, it only uses the alt text so only particularly long alt text causes problems. It may happen with other versions of Outlook than 2003, I haven't tested, or various other mail clients that block images as a protective measure.