List hygiene is a crucial part of succeeding in email marketing. It's important to know how to use a win-back campaign to not only re-engage your users but also to maintain a healthy and active email list. The formula I’ve learned to love when it comes to a win-back campaign is: the right message + careful timing = a successful win-back campaign.Creating the right message is rather simple. Offering a discount is common knowledge but which type of discount performs better? Do you offer a certain percentage off or give a hard dollar value as a discount? A study done by Return Path shows that offering recipients a dollar amount off in the subject line leads to twice the amount of opens compared to providing a percentage off. Other common phrases used were “we miss you,” “come back,” and “{CUSTOMER_NAME}, was it something we said?” As for the email template itself, a short email template with a clear call-to-action button will go a long way.Unfortunately, having the right message alone will not make a re-engagement campaign successful. When it comes to sending offers at the right time, there are a lot of factors that are not in our hands, such as personal affairs in your recipient's lives. For this reason, I’ve found sending follow up emails can lead to higher chances of re-engagement. Sending a total of three to four win-back campaigns spread out within several days or even weeks will give you a better chance to reach your recipient in a better state of mind.However, it’s crucial that if your users do not show any activity after four attempts that you unsubscribe them from your list. Inactive email accounts are commonly converted into spam traps by Email Service Providers (ESP). This is their way of seeing if email marketers are keeping their list up-to-date. As much as employers may hate doing this, it’s arguably the most important part of the equation.When creating a win-back campaign, it’s always good to remember to make the email template short and simple. Include a clear call-to-action button and don’t give up if your first win-back campaign fails to meet your expectation.A final tip I can provide is to send your win-back campaigns in smaller chunks while monitoring your complain rate closely. The last thing you want is a spike in complaints leading to poor email deliverability.