Validating email addresses involves a multi-faceted approach, considering both syntax and deliverability. Experts and documentation sources agree that modern email syntax is complex, allowing for special and internationalized characters (Unicode). While regular expressions can check syntax, overly strict patterns are discouraged as they may reject valid addresses. A more reliable approach involves deliverability checks, such as sending confirmation emails and monitoring bounces. Email validation services offer comprehensive checks, including syntax, domain existence, mailbox existence, and spam trap detection. Marketers also highlight the importance of typo detection, plus addressing, and detecting disposable email addresses to maintain list quality and sender reputation.

Validating email addresses involves ensuring they adhere to the correct structure and are deliverable. Techniques range from simple syntax checks using regular expressions to more sophisticated methods like sending confirmation emails and detecting disposable addresses. Valid email addresses can include alphanumeric and special characters, and many services support plus addressing (e.g., yourname+keyword@example.com). Real-time typo detection helps prevent errors during email capture. Email validation is crucial for maintaining a clean email list, improving deliverability, and protecting sender reputation. It helps prevent bounces, spam complaints, and blacklisting.

Experts emphasize the complexity of email address syntax, noting the allowance of special and internationalized characters. Overly strict validation using regular expressions is discouraged. Instead, a focus on deliverability checks, such as sending test emails and monitoring bounces, is recommended to ensure an email address is valid and accepting mail. Modern email addresses can also have full unicode in the domain including internationalized TLDs.

Documentation sources highlight various approaches to email address validation. IETF's RFC 5322 defines the formal syntax, detailing allowed characters and structure. MSDN provides an example using .NET regular expressions but acknowledges limitations, such as TLD validation. OWASP advises against overly strict regex validation due to complexity, recommending relaxed patterns or email confirmation. Verimail emphasizes comprehensive validation services that check beyond syntax, including domain, mailbox existence, and spam trap detection for deliverability.