What does Decay Protection do?
If "Decay Protection" is checked, that means mailfloss will automatically verify your entire connected email service provider email database every month as a default (or depending on your selected schedule), preventing existing emails from going stale (on average, emails go stale at a rate of 2.1% per month because of job turnover, abandoned addresses and domains, etc).
This is recommended in order to keep your list protected from email decay. If you combine that with autofloss and an auto action, such as automatic unsubscribe or automatic delete, you have a completely hands-off and automated approach to email verification. This is what many of our customers do, what we do ourselves, and why mailfloss was built. Talk about convenient! :)
It can be enabled from the Frequency options under the Integrations section in the mailfloss app.