email

auth/email — validation, normalization, DNS MX

Validate + normalize an address in one call, optionally verify its domain can receive mail.

Run

go run ./examples/email

The VerifyDomain step performs a real DNS lookup. It is skipped automatically if your network has no outbound DNS access.

What it shows

Expected output (abridged)

=== ValidateAndNormalize ===
accepted  "  USER@EXAMPLE.COM  " → "user@example.com"
accepted  "user.name+tag@sub.example.co.uk" → "user.name+tag@sub.example.co.uk"
rejected  "" → must not be empty
rejected  "notanemail" → invalid format
rejected  "user@localhost" → domain must contain at least one dot
rejected  "user@example..com" → invalid format

=== VerifyDomain ===
domain OK     : user@gmail.com

=== Error handling ===
ErrInvalidEmail: email: invalid address: invalid format
reason only   : invalid format

Golden rule

Always normalize before storing and before querying the database. User@EXAMPLE.COM and user@example.com are the same address — store only the canonical form.