When to send it
Use this when you have more candidate features than time and want customers to help you choose. A good moment is a few weeks before you plan the next quarter or the next big build. Email it to active customers, and show it inside the product as well, so busy users who never open your emails still get a say.
Before you send it, replace the six options in the ranking question with your own candidates. Keep each one short and describe the outcome rather than the implementation: "Share reports with clients" is easier to judge than "PDF export API". Four to six options is the comfortable range. Beyond that, people order the top few with care and drop the rest in any order.
Why ranking
Asking people to rate each idea separately invites them to mark everything as important. Ranking forces trade-offs, which is exactly the decision you're facing. In analytics, Hearsay sorts the options by their average position and shows how often each was put first, so you see not only the winner but how close the runners-up are.
A ranking alone doesn't tell you why, so the second question asks what their first choice would let them do. Those answers often reveal a simpler way to solve the same problem than the feature you listed.
The next question asks whether something more important is missing from the list, and those who say yes describe it. This guards against the classic mistake of a priority survey: asking people to choose between your ideas when their real need isn't on the list at all.
The last question asks how often they use the product. A feature ranked first by daily users and last by occasional ones tells a different story from one that everyone places in the middle.
No coupon here
A coupon would draw in people who rarely use the product, and their rankings would count as much as those of your most engaged customers. The reward for answering is a product that improves in the direction they asked for.
What to do with the answers
Export the responses and split the rankings by usage frequency first. Daily users usually deserve the most weight, because they're the ones who stay and pay. Read the "why" answers for the top two options and write the underlying job down in one sentence each.
Treat the result as an input, not a vote. If the same write-in idea appears several times, test it with a short problem discovery survey before committing. After you build the winner, follow up with Feature feedback to check it landed, and tell everyone who took part what you chose and why.