What is a “risky” email address?

A risky address is one that won't hard bounce but will absolutely mess with your metrics. It looks valid, it receives mail, and then... nothing. No opens, no engagement, no signal. Sometimes worse: it marks you as spam.

Here's the distinction that matters. A toxic address will destroy your reputation (spamtraps, breached accounts). A risky address just quietly drags down your performance. You'll keep sending to it, see zero response, and watch your overall engagement rate tank as a result.

Common risky addresses include catch-all domains (company.com accepts mail to anyone@company.com, so you don't know if it's real), role-based accounts (info@, support@, help@) that change hands constantly, old corporate domains from companies that downsized or changed email providers, temporary forwards that expired, and inactive users who haven't engaged in a year or more.

The mechanism is engagement-based filtering. Modern mailbox providers (Gmail, Outlook, Yahoo) don't just check sender reputation. They watch engagement. If you're sending to addresses that never open or click, providers notice the pattern. They treat future mail from you more skeptically. One inactive subscriber isn't a problem. But if 20% of your list is inactive? That affects how providers route all your mail.

The solution isn't to nuke risky addresses entirely (though you can if you want to be aggressive). Try a re-engagement campaign first: three emails over four weeks offering something of value, then remove anyone who doesn't respond. This salvages some subscribers and cleans up your list. For new signups, ask for individual email addresses instead of catch-all or role-based ones. And audit your list every few months to flag the inactive folks.