diff --git a/HowtoPostfix.md b/HowtoPostfix.md
index 767deb2a..a0a70069 100644
--- a/HowtoPostfix.md
+++ b/HowtoPostfix.md
@@ -1721,4 +1721,8 @@ ou alors de façon plus globale le paramètre `default_process_limit` :
 default_process_limit = 500
 ~~~
 
+### Header Checks
+
+<https://www.sweetnam.eu/index.php/Postfix_Header_Checks>
+<https://mailing.postfix.users.narkive.com/GiWF2O9k/encoded-subjects-aren-t-rejected-by-header-checks>