The most common way businesses do this is the following:

1.) Create an HTML-based email layout.
2.) Host your image(s) on your public server
3.) “Hotlink” your images using
4.) Wrap a hyperlink around the image using image

This, of course, assumes you have some experience working in HTML.

If you are a smaller business, and not looking to do anything quite so fancy, you can attach your coupon in your email message, and add a text link into the body of the email. Keep in mind that when it comes to email marketing, what you see is not always what the customer gets. Varying email clients interpret emails very differently. Your email may look great in Entourage, but it may break badly in Hotmail or some other email service… and a bad/broken email may do more harm than good for your brand. If you are not experienced in HTML and/or email marketing, I recommend you keep it as simple as possible.

Lastly, if you are in the US, you are subject to the CAN-SPAM Act of 2003, which puts specific restrictions on email-based marketing. For example, you must allow customers to opt-out of mailings. Read more here:

Oh, and if this wasn’t obvious, you should never expose your recipient’s email addresses! Use a service like mailchimp.com, ConstantContact, vertical response, or at least BCC everyone on your distribution.