I have received many mails in which people advertise their business through images and there is no attachment. How they do that, I mean how they insert image in the mail without attachment?
After some research i have found that its very simple to do it.
Just like you would insert it in any other HTML document.
<img src="http://LinkToTheImage.com/image.jpg" width="X" height="Y" alt="My Image" />
Where, of course, http://LinkToTheImage.com/image.jpg is the link to an image you host somewhere on your server or image hosting service.
for example [Google picasa] just upload a picture in your google+ profile and get the URL.
Just Try it.