Definition
Email validation checks whether an address could be valid. It looks at the format of the address and at the domain, without asking a mail server about the specific mailbox.
Typical validation steps:
- The address has one @, a local part and a domain part.
- The characters are allowed, and the length limits hold (64 octets for the local part, about 254 for the whole address in practice).
- The domain exists in DNS.
- The domain has MX records, or at least an A record mail could fall back to.
- The domain is not a known misspelling of a popular provider.
Many teams use "validation" and "verification" as synonyms, and plenty of tools do too. When the difference matters, verification means going one step further and checking that the mailbox itself accepts mail.
Why it matters
Validation is fast and cheap, so it belongs everywhere an address is collected. A regex or the browser's built-in type="email" check catches obvious junk the moment it is typed. A DNS lookup catches domains that do not exist.
It is not enough on its own. An address like [email protected] passes every validation check even if Jane left the company two years ago. Only a mailbox check can tell you that, and even then catch-all domains limit what is knowable.
A practical setup: validate in the browser for instant feedback, then verify on the server before you create the account or add the contact to a campaign.
How SimpleCold handles it
Validation steps run first in SimpleCold's pipeline: normalising the address, checking syntax, then checking the domain and its MX records. Failures there come back Undeliverable with invalid_format or no_mail_server and never reach a mail server. If the domain looks like a typo of a common provider, the status is possible_typo and the result includes a suggestion. Addresses that pass go on to the mailbox check.
Try the free email syntax checker for format-only checks.