Yes, I am sure I want to reply to this message because I had the exact same issue. I want to thank the original poster for starting the thread. I was getting "motion detection" alert emails but not actual images. And yes, the solution proposed by the original poster has to do with the "Username" field in the advanced settings of the cameras configuration. However, my problem wasn't solved until I entered the "Username" as the exact "opposite" of what the OP was suggesting. I had entered "only" the first part of my email address without the @xxx.com portion. When I changed it to the full email address it began working correctly again, i.e., I got actual image attachments that I wasn't getting before.
So, if you have a similar issue, i.e., you are not receiving image attachments, try using both the username portion of your email address and the full email address. One of these should make it work, probably the opposite of whatever you have it configured to use in it's non-working state.