Email Validator Guide: Syntax, Domains and Form QA
Email validation looks simple, but real forms fail when they reject valid addresses, accept obvious typos or hide unclear errors. A good validator should help users complete the form, not fight them.
What an email validator should check
Start with structure: one local part, one @ symbol and a domain with at least one dot. Then check for spaces, invalid punctuation, repeated dots and domain patterns that are usually incomplete.
Syntax validation is not deliverability
A browser tool can tell you whether an address looks valid, but it cannot guarantee the inbox exists. Treat syntax validation as a fast QA step before deeper verification, confirmation emails or CRM imports.
Common form mistakes
- Rejecting long top-level domains.
- Blocking plus aliases such as
name+tag@example.com. - Accepting addresses with spaces copied from spreadsheets.
- Showing vague errors like "invalid input" instead of actionable feedback.
QA checklist
Test normal addresses, plus aliases, subdomains, uppercase characters, pasted whitespace and common typos. The best validation flow trims harmless spacing, flags risky patterns and gives users a clear next step.