diff --git a/mailvalidate/validation.go b/mailvalidate/validation.go
index 85bf44c..193285f 100644
--- a/mailvalidate/validation.go
+++ b/mailvalidate/validation.go
@@ -251,11 +251,12 @@ func handleSmtpResponses(resp EmailValidation) EmailValidation {
 			resp.SmtpSuccess = true
 			resp.ErrorCode = ""
 			resp.Description = ""
-		}
-		if resp.ErrorCode == "5.2.1" || resp.ErrorCode == "5.7.1" || resp.ErrorCode == "5.1.1" || resp.ErrorCode == "5.1.6" || resp.ErrorCode == "5.1.0" || resp.ErrorCode == "5.4.1" {
+		} else if resp.ErrorCode == "5.2.1" || resp.ErrorCode == "5.7.1" || resp.ErrorCode == "5.1.1" || resp.ErrorCode == "5.1.6" || resp.ErrorCode == "5.1.0" || resp.ErrorCode == "5.4.1" {
 			resp.SmtpSuccess = true
 			resp.ErrorCode = ""
 			resp.Description = ""
+		} else if resp.ErrorCode == "5.7.511" {
+			resp.RetryValidation = true
 		}
 	case "554":
 		if resp.ErrorCode == "5.7.1" {