diff --git a/email.go b/email.go
index 1d1fb53..3856599 100644
--- a/email.go
+++ b/email.go
@@ -30,8 +30,44 @@ func IsEmail(email string) Result {
 		return ResultNotEmail
 	}
 
-	user := email[:atIndex]
+	return isValidEmailUser(email[:atIndex])
+}
+
+// makeEmail makes a checker function for the email checker.
+func makeEmail(_ string) CheckFunc {
+	return checkEmail
+}
+
+// checkEmail checks if the given string is an email address.
+func checkEmail(value, _ reflect.Value) Result {
+	if value.Kind() != reflect.String {
+		panic("string expected")
+	}
+
+	return IsEmail(value.String())
+}
+
+// isValidEmailDomain checks if the email domain is a IPv4 or IPv6 address, or a FQDN.
+func isValidEmailDomain(domain string) Result {
+	if len(domain) > 255 {
+		return ResultNotEmail
+	}
+
+	if domain[0] == '[' {
+		if strings.HasPrefix(domain, ipV6Prefix) {
+			// postmaster@[IPv6:2001:0db8:85a3:0000:0000:8a2e:0370:7334]
+			return IsIPV6(domain[len(ipV6Prefix) : len(domain)-1])
+		}
+
+		// postmaster@[123.123.123.123]
+		return IsIPV4(domain[1 : len(domain)-1])
+	}
+
+	return IsFqdn(domain)
+}
 
+// isValidEmailUser checks if the email user is valid.
+func isValidEmailUser(user string) Result {
 	// Cannot be empty user
 	if user == "" || len(user) > 64 {
 		return ResultNotEmail
@@ -79,36 +115,3 @@ func IsEmail(email string) Result {
 
 	return ResultValid
 }
-
-// makeEmail makes a checker function for the email checker.
-func makeEmail(_ string) CheckFunc {
-	return checkEmail
-}
-
-// checkEmail checks if the given string is an email address.
-func checkEmail(value, _ reflect.Value) Result {
-	if value.Kind() != reflect.String {
-		panic("string expected")
-	}
-
-	return IsEmail(value.String())
-}
-
-// isValidEmailDomain checks if the email domain is a IPv4 or IPv6 address, or a FQDN.
-func isValidEmailDomain(domain string) Result {
-	if len(domain) > 255 {
-		return ResultNotEmail
-	}
-
-	if domain[0] == '[' {
-		if strings.HasPrefix(domain, ipV6Prefix) {
-			// postmaster@[IPv6:2001:0db8:85a3:0000:0000:8a2e:0370:7334]
-			return IsIPV6(domain[len(ipV6Prefix) : len(domain)-1])
-		}
-
-		// postmaster@[123.123.123.123]
-		return IsIPV4(domain[1 : len(domain)-1])
-	}
-
-	return IsFqdn(domain)
-}