1 files changed, 5 insertions, 0 deletions

diff --git a/conf.d/040_transports.conf b/conf.d/040_transports.conf
index 94d9b88..5a2d389 100644
--- a/conf.d/040_transports.conf
+++ b/conf.d/040_transports.conf
@@ -26,6 +26,11 @@ remote_smtp:
 # The "Sender" header is excluded from the signature process, allowing mailing list
 # servers to forward messages without invalidating the signature.
 # ref: https://www.spinics.net/lists/linux-media/msg138870.html
+
+.ifndef _DKIM_SIGN_HEADERS
+_DKIM_SIGN_HEADERS = In-Reply-To:Content-Transfer-Encoding:Content-Type: MIME-Version:References:Message-ID:Subject:To:From:Date:Sender:Reply-To:Cc: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive
+.endif
+
 signed_smtp:
   driver             = smtp
   message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}