diff --git a/target/postfix/sender_header_filter.pcre b/target/postfix/sender_header_filter.pcre
index cc0a79ab..fe4ff045 100644
--- a/target/postfix/sender_header_filter.pcre
+++ b/target/postfix/sender_header_filter.pcre
@@ -8,4 +8,4 @@
 /^\s*X-Mailer/                      IGNORE
 /^\s*X-Originating-IP/              IGNORE
 /^\s*Received: from.*127.0.0.1/     IGNORE
-
+/^Content-Type:/i                   PREPEND X-MS-Reactions: disallow