Email Address Validator

Email Address Validator: RFC-Compliant Syntax Checking

Invalid email addresses are one of the most preventable causes of hard bounces. Whether from typos at signup, data import errors, or list decay over time, addresses that fail basic syntax checks will never deliver and will hurt your sender reputation every time you try. This validator checks RFC 5321/5322 compliance and optionally verifies domain MX records for domains that pass syntax validation.

Common Email Validation Failures

• Missing @ symbol — The most basic error. Sometimes caused by form field confusion during data entry
• Domain without TLD — user@domain instead of user@domain.com
• Consecutive dots — john..doe@example.com violates RFC 5321
• Local part over 64 characters — Very long usernames exceed the RFC limit
• Domain has no MX record — The domain exists but isn't configured to receive email
• Spaces in address — john doe@example.com is not a valid address

List Validation Best Practices

Validate at signup (real-time API validation), validate before importing to a new ESP, and validate your full list at least annually. Combine syntax validation with regular suppression of hard bounces and list hygiene analysis to maintain a clean, deliverable list. A clean list is fundamental to maintaining good IP reputation and low bounce rates.