add list headers - List-Id may not be needed

cropswap-sendmail.sh

@@ -22,7 +22,14 @@ subject="$(formail -cx "Subject:" < "${WD}/mail")"
 if [ "${subject/\[${SUBJECT}\]/}" == "${subject}" ]; then
 	subject="[${SUBJECT}] ${subject## }"
 fi
-formail -I "Subject: ${subject}" < "${WD}/mail" | tail -n+2 > "${WD}/mail.new"
+formail \
+	-I "Subject: ${subject}" \
+	-I "List-Id: $MAILGROUP" \
+	-I "List-Unsubscribe: <mailto:$MAILGROUP?subject=[UNSUBSCRIBE]>" \
+	-I "List-Subscribe: <mailto:$MAILGROUP?subject=[SUBSCRIBE]>" \
+	-I "List-Post: <mailto:$MAILGROUP>" \
+	-I "List-Unsubscribe-Post: List-Unsubscribe=One-Click" \
+< "${WD}/mail" | tail -n+2 > "${WD}/mail.new"
 mv "${WD}"/mail{.new,}
 
 declare -A SUBSCRIBED