diff --git a/Log-Bounce.md b/Log-Bounce.md
index e24bca4..676b7ef 100644
--- a/Log-Bounce.md
+++ b/Log-Bounce.md
@@ -110,3 +110,13 @@ from localhost [127.0.0.1]
 550 5.1.1 <quynh-vuvan@gate.sws.co.jp>... User unknown
 <<< 554 no valid recipients given
 ```
+
+### Lỗi cần chú ý
+
+* Subject: Delivery Status Notification (Failure)
+
+```
+The following message to <hddt.cks@gmail.com> was undeliverable.
+The reason for the problem:
+5.3.0 - Other mail system problem 550-"5.7.1 [125.235.240.53 11] Our system has detected that this message is\n5.7.1 not RFC 5322 compliant:\n5.7.1 'From' header is missing.\n5.7.1 To reduce the amount of spam sent to Gmail, this message has been\n5.7.1 blocked. Please visit\n5.7.1 https://support.google.com/mail/?p=RfcMessageNonCompliant\n5.7.1 and review RFC 5322 specifications for more information. q88si877649pja.61 - gsmtp"
+```