What Is Email Syntax Validation?
Email syntax validation checks whether an email address follows the correct format rules defined in internet standards (RFC 5321 and RFC 5322). It's a quick, inexpensive check that catches obviously invalid addresses before more complex validation steps.
The Anatomy of a Valid Email Address
A valid email address has two parts separated by the @ symbol:
local-part@domain
For example, in john.smith@company.com:
- Local part: john.smith
- @ symbol: Required separator
- Domain: company.com
Rules for the Local Part
The local part (before the @) must follow these rules:
- Maximum 64 characters
- Can contain: letters, numbers, dots, hyphens, underscores, plus signs
- Cannot start or end with a dot
- Cannot have consecutive dots (..)
- Special characters allowed only if quoted
Rules for the Domain Part
The domain (after the @) must follow DNS naming rules:
- Maximum 255 characters total
- Each label (between dots) maximum 63 characters
- Must contain at least one dot
- Top-level domain must be at least 2 characters
- Can contain letters, numbers, and hyphens
- Cannot start or end with a hyphen
Common Syntax Errors We Catch
ValidateList's syntax validation catches these frequent mistakes:
- Missing @ Symbol: johncompany.com
- Multiple @ Symbols: john@@company.com
- Spaces in Address: john smith@company.com
- Invalid Characters: john[smith]@company.com
- Missing Domain: john@
- Consecutive Dots: john..smith@company..com
Why Syntax Validation Isn't Enough
While syntax validation catches obvious errors, it has limitations. An address like xyz123@gmail.com is syntactically valid but may not exist. That's why ValidateList performs multiple validation steps beyond syntax checking.
Try It Free
ValidateList performs comprehensive syntax validation as part of our free bulk email validation. Upload your list and see how many addresses fail basic format checks.