I just want to share a method with you that I found to be very effective when promoting affiliate products to my list.
It's more powerful than sending a purely promotional email. Here it is:
Before promoting the product in your email, give them a free branded report. You could ask the merchant if he has a report you can brand with your affiliate link; or if not, ask their permission to compile their articles into a short e-book.
Give your list the report first, then below that you could promote the related product. This is powerful because you're giving them something for free, with no strings attached whether they buy the actual product or not. (This uses the law of reciprocity).
At the same time, the report might go viral and they will buy the product if it's truly helpful. If they don't buy immediately, they could in the future because they'll come back to read the report any time in the future. (This doesn't happen very often with emails.)
But you could take it one step further. Ask the merchant if he can give your subscribers an exclusive, time-sensitive discount. I often do that when JVing with other marketers because my subscribers are much more responsive to time-limited, special offers. The law of scarcity really works!
We may have lost a certain commission amount per sale, but the quantity of the orders multiply significantly! This works for my list, but I'm not sure it would work with yours. So the key is to always TEST, TEST, AND TEST.
So to recap, give a free report first, then present your time-sensitive special offer after that. (yes, this is in one email).
Best of luck,