You can use what is called “image maps” in HTML. To learn more: click here

However, this technique is not recommended for 2 reasons:

• Some webmails interpret MAPS in a strange way. Since the coordinates are relative, they take the upper left corner of the web page as the reference point instead of the upper left corner of the message! As a result, all clickable parts end up being shifted…
• Some antispam filters are sensitive to the presence of MAPS and will penalize the message more easily by classifying it as spam.

Another important point: to reduce the “spam score,” it is recommended to balance the ratio of images to text in your message. => See rule #2 in the following article: How can I prevent my messages from ending up in spam or being blocked by an anti-spam filter?