diff --git a/cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup b/cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup
index 69a537db..1f21b41e 100644
--- a/cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup
+++ b/cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup
@@ -1,3 +1,4 @@
 /^From:/            DUNNO
 /^Message-Id:/      DUNNO
+/^Chat-Is-Post-Message:/      DUNNO
 /.*/                IGNORE