MailboxValidator

MailboxValidator has verified billions of emails since 2010, using SMTP probes to confirm that mailboxes actually exist on their target servers. The service catches typos, detects disposable and temporary providers, and flags known spam traps before they hit your list.

It's a solid pick if you need straightforward verification without vendor lock-in. The API supports both single email checks and large batch uploads, and pricing is per-email checked, making it cost-predictable for list cleaning at any scale.