Email verification APIs

Whether you're cleaning an existing email list or validating addresses at signup, email verification services help you reduce bounces, protect your sender reputation, and ensure your emails actually reach real inboxes. These services check whether an email address is valid, deliverable, and safe to send to.

Common use cases include:

• Cleaning your subscriber list before a big campaign to improve your deliverability
• Validating emails at signup to prevent typos and fake addresses
• Detecting disposable email addresses that users create just to grab a freebie

Most of these services work similarly: they check syntax, verify the domain has valid MX records, and attempt to verify whether the mailbox actually exists without sending an email. The main differences come down to pricing, accuracy claims, and integration options.

Any other noteworthy alternatives?

• Abstract offers a simple API-first approach with a generous free tier of 100 verifications per month.
• Mailfloss is designed specifically for automated list cleaning with direct integrations to major ESPs like Mailchimp and ActiveCampaign.
• Truemail provides both real-time verification and bulk list cleaning with competitive pricing for high-volume users.
• If you're already using an email service provider like Mailchimp or SendGrid, check whether they offer built-in list cleaning tools before adding another service.

Why does this matter for newsletter authors?

High bounce rates hurt your sender reputation, which means more of your emails end up in spam folders. If you're migrating an old list to Buttondown or haven't emailed your subscribers in a while, running your list through a verification service first can save you headaches down the road.

Gee, it sure is awfully nice of you to compile this resource and keep it up to date. What can I ever do to thank you?

Tell your friends about Buttondown, the best way to start and grow your email newsletter.