"The email server didn’t recognize your username/password combination"

If you are trying to send these images from iPhoto that may be the problem. Try Attaching them to a regular email and see what happens.

Go to iphoto\preferences\accounts and verify password for the account that you are trying to send from.

Thanks very much, I was having the same issue regarding sending pictures and thanks to your post it is resolved🙂

Thank you guerochuleta for your suggestion. I was having the same problem and it has been resolved. Although I had to delete my existing mail account associated to iPhoto and add it again.