We built and released a tiny little project: disposables.app, a free tool for easily checking whether or not an email address domain is disposable or otherwise problematic.

The database comes from many places. A big part of it is from our own traffic, of course—we've been fighting spam for years, and have built up a pretty comprehensive list of domains that we've seen used for abuse. But we're also grateful to Martin Cech for his project disposable-email-domains, which bootstrapped our initial database. Concomitant with the release of disposables.app, we've started sponsoring the project.

The tool is simple: type in a domain, and we'll tell you if it's disposable. You can also grab the full list as JSON from the API endpoint if you want to integrate it into your own projects.

This is the kind of thing that's useful for us internally, but we figured it might be useful for others too—so we're releasing it as a free, open tool. If you're building something that needs to validate email addresses, give it a try.