How to verify emails at signup without blocking real users (Node.js)
Most signup forms validate an email with a regex and call it done. That catches bob@@gmail but happily accepts jane@compnay.com , test@mailinator.com and ceo@a-domain-that-accepts-everything.com . A month later your welcome emails are bouncing and your sender reputation is paying for it. Here's a small, practical pattern for checking addresses at signup without blocking real users. The code uses…
Verifying email addresses during signup is crucial to avoid bounced welcome emails and maintain a good sender reputation. While many forms only validate email syntax, this misses potential issues. A real check examines the domain's mail server to see if the mailbox exists without sending anything. There are five possible outcomes: valid mailbox, invalid, mailbox can't receive mail, risky disposable or shared inbox, and catch-all domain.
It's essential not to block signups for catch-all or unknown domains, as these are used by real companies and mail servers may not respond to verification probes. The provided Node.js code demonstrates how to check an email address using the ListCheckup API. It sets a timeout of four seconds, handles potential errors, and returns the appropriate action based on the result.
If the service is unavailable or times out, the signup should still be accepted to avoid disrupting the user funnel. The code also suggests storing a flag in the user record for future reference, such as determining which users get the first newsletter.
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