How long before ISPs deactivate idle inboxes?

You've probably got subscribers on your list who haven't opened anything in over a year. Maybe two years. And somewhere in that group, some of those email accounts no longer exist. When an inbox goes dormant long enough, the provider shuts it down. Then things get interesting for your sender reputation.

Here's how the major providers handle it, roughly speaking. Gmail and Outlook.com typically give accounts two years of inactivity before taking action. Yahoo Mail has historically used a 12-month threshold, though the exact policy shifts over time. AOL Mail follows similar logic to Yahoo since they share the same parent company.

Corporate accounts are a different story. When someone leaves a company, their IT team often disables or deletes the mailbox within days or weeks, not months. That B2B list you built two years ago? It's probably dirtier than you think.

What counts as "activity" varies too. Logging into webmail counts. Sending an email counts. Some providers count receiving mail as activity, which means your campaigns might accidentally be keeping accounts just barely alive. Don't count on it though. You sending to someone is not the same as that person using their account.

The real deliverability risk kicks in after deactivation. Providers can recycle old addresses and reassign them to new users, or convert them into inactive account traps that flag any sender still mailing to them. If you're still hitting those addresses, you're telling spam filters you don't clean your list. That's a reputation hit you don't want.

The practical takeaway: if a subscriber hasn't engaged in 12 months, treat them as high-risk. By 18 to 24 months of silence, they're very likely gone or recycled. A proper sunset policy should catch them before the provider does.

If you're not sure how much decay is hiding in your list, we clean lists at RME (hi ;)) and flag addresses that have gone quiet long enough to be risky. Worth a look before your next big campaign.