From db69c29c06d7e29003351bb0cfe33af4c7ecd8d3 Mon Sep 17 00:00:00 2001
From: feld <40271278+feld@users.noreply.github.com>
Date: Fri, 5 Jun 2026 13:31:17 -0700
Subject: [PATCH] Revert "Revert "Aggressive LMTP header cleanup (#816)""

This reverts commit 6def189d16143978b004c18e38d7ae4b3aa474ac.
---
 .../src/cmdeploy/postfix/lmtp_header_cleanup  | 26 ++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup b/cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup
index 3c45f8d8..8b3cf2e7 100644
--- a/cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup
+++ b/cmdeploy/src/cmdeploy/postfix/lmtp_header_cleanup
@@ -1,3 +1,23 @@
-/^DKIM-Signature:/            IGNORE
-/^Authentication-Results:/            IGNORE
-/^Received:/            IGNORE
+# List of headers for incoming messages 
+# that must be retained for functionality and compatibility reasons 
+/^From:/            DUNNO
+/^Message-Id:/      DUNNO
+/^Chat-/            DUNNO
+/^Content-Type:/    DUNNO
+
+# For receiving clear-text messages (still supported in May 2026)
+/^Subject:/         DUNNO
+/^Date:/            DUNNO
+/^To:/              DUNNO
+/^CC:/              DUNNO
+/^References:/      DUNNO
+/^In-Reply-To:/     DUNNO
+
+# Senders might support Autocrypt 1 but not RFC9788 (Header Protection) 
+/^Autocrypt:/       DUNNO
+
+# SecureJoin V2 protocol headers (for backward compatibility) 
+/^Secure-Join/      DUNNO
+
+# Ignore all other headers
+/.*/                IGNORE