How email validator works
Email validation checks that an address follows the correct format according to the relevant RFCs: a local part, an @ symbol, and a domain with at least one dot and a valid top-level domain. It does not verify that the mailbox actually exists or can receive mail — only that the address is syntactically possible.
This validator uses a regular expression that checks the local part (letters, digits, and common punctuation including + for plus-addressing), the @ symbol, and a domain made of valid labels separated by dots, each not starting or ending with a hyphen. On success it returns the local and domain parts; on failure it gives a plain-English reason such as "missing @ symbol" or "multiple @ symbols".
Use it to catch typos in sign-up forms, clean a contact list before import, or guard an API against obviously bad input. For true delivery verification you need to send a confirmation email — syntax validation is only the first filter.