Engineering
Deliverability guides and product notes — no filler.
How to validate an email address in PHP
PHP email validation done right: filter_var for syntax, checkdnsrr/getmxrr for MX, and an API for the SMTP mailbox check. Working code for each layer.
Email verification API comparison for developers
How to choose an email verification API: verdicts and evidence, sync vs async, bulk and webhooks, rate limits, EU data — and the options compared.
Building email bounce classification
Build an email bounce classifier: map SMTP and enhanced codes to suppress or retry, spot policy blocks, and classify addresses before they bounce.
Verify email at signup with a serverless function
Verify email at signup with a serverless function: reject typos and dead domains at the door, keep your API key server-side, and fail open.
How to validate an email address in Python
Validate an email address in Python properly: syntax, an MX lookup with dnspython, and the SMTP mailbox probe — with working code.
How to validate an email address in Ruby
Validate an email address in Ruby in three layers: URI::MailTo syntax, a Resolv MX lookup, and an SMTP mailbox check via API, with working code.
How to validate an email address in Go
Validate an email address in Go the right way: net/mail.ParseAddress for syntax, net.LookupMX for MX, and an API for the SMTP mailbox check.
How to validate an email address in Java
Validate an email address in Java: Jakarta Mail syntax checks, a safe regex, an MX lookup via JNDI and an SMTP mailbox check, with working code.
How to validate an email address in C#
Validate an email address in C# the right way: MailAddress for syntax, DnsClient for the MX lookup, and an API for the SMTP mailbox probe.
Validate an email address in Laravel, from rule to mailbox
Validate an email address in Laravel with the email:rfc,dns rule, then confirm the mailbox with a verification API from a custom validation rule.
How to validate an email address in Django
Validate an email address in Django properly: EmailField for syntax, an MX lookup with dnspython, and an API for the SMTP mailbox check.
How to validate an email address in Node.js
Validate an email address in Node.js properly: a syntax check, an MX lookup with node:dns, and the SMTP mailbox probe — with working code.