Email Address (RFC 5321 Simplified) Regex for Go

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching email address (rfc 5321 simplified), ported and verified for Go. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// Email Address (RFC 5321 Simplified)
// ReDoS-safe | RegexVault — Web & Network > Misc

package validation

import "regexp"

var emailAddressRfc5321SimplifiedRe = regexp.MustCompile(`^[a-zA-Z0-9.!#$%&'*+/=?^_`{|}~\-]{1,64}@[a-zA-Z0-9](?:[a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?(?:\.[a-zA-Z0-9](?:[a-zA-Z0-9\-]{0,61}[a-zA-Z0-9])?)*\.[a-zA-Z]{2,63}$`)

func ValidateEmailAddressRfc5321Simplified(s string) bool {
    return emailAddressRfc5321SimplifiedRe.MatchString(s)
}

// Example
// fmt.Println(ValidateEmailAddressRfc5321Simplified("user@example.com")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > Misc category and carries a ReDoS-safe certification. That matters for Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Full RFC 5321 compliance is extremely complex. This covers 99%+ of real-world email addresses. Local part limited to 64 chars per RFC 5321 section 4.5.3. Always send a confirmation email to verify — regex alone cannot confirm deliverability.