Nick Usborne recently wrote an article called "Where and how to place your links in a 2-column HTML email".
These are the tips he offers:
- Links in the side columns will not perform as well as those in the center column, even if they are accompanied by nice product photos.
- In the main column a simple best practice is to place a text link early on in the text as well as at the end.
- When writing the text links, a descriptive link will usually out-perform a shorter, instructional link. In other words, “save 20% on our end-of-season Sea Kayaks” will likely do better than “buy now” or even “check out our low prices”.
- If you are selling more than one product in your email, you will probably get a higher click-through on the first product mentioned, and the lowest click-through on the last. (This is generally true, but definitely not true all of the time.)
He does add that "the best practices I describe are true of what I have seen overall. That said, I also see metrics on emails that fly in the face of all these suggestions."
So you should still test what works best for your audience.