Keyonna Howcott is a Digital Strategist for the United Way of Central Maryland. She switched her organization over to ActiveCampaign and immediate used it to clean her lists by using a free template, called a recipe, in ActiveCampaign - Engagement Tagging (Parts 1 and 2).
This automation pushes contacts through a set of rules that show if the contact is engaged. That can be if they visit your website, open an email, click a link, as well as other options.
This is a great way to keep a clean list, improve your deliverability, and give you t5he opportunity to send those people that are less engaged emails that actually want to open.