Add header tag creation.

This will create a tag in email headers that can be used for filtering by receiving servers. I use this image for relaying through exchange online, and the nature of how I run my containers prevents me from setting static IPs as a filter. With a tag for exchange to look at, I can make sure emails from the relay are not hitting the junk folder.

Without setting the HEADER_TAG variable, the script will create a randomly generated tag and move on. It is not a requirement to make use of this feature.

run.sh

@@ -46,5 +46,26 @@ if [ ! -f /etc/postfix/sasl_passwd ]; then
   fi
 fi
 
+#Set header tag
+postconf -e "header_checks = regexp:/etc/postfix/header_tag"
+if [ -z "${HEADER_TAG}" ]; then
+TAG="$RANDOM"
+else
+TAG="${HEADER_TAG}"
+fi
+echo -e "/^MIME-Version:/i PREPEND RelayTag: $TAG\n/^Content-Transfer-Encoding:/i PREPEND RelayTag: $TAG" > /etc/postfix/header_tag
+echo "******** Header tag is $TAG *********"
+
+# Create sasl_passwd file with auth credentials
+if [ ! -f /etc/postfix/sasl_passwd ]; then
+  grep -q "${SMTP_SERVER}" /etc/postfix/sasl_passwd  > /dev/null 2>&1
+  if [ $? -gt 0 ]; then
+    echo "Adding SASL authentication configuration"
+    echo "[${SMTP_SERVER}]:${SMTP_PORT} ${SMTP_USERNAME}:${SMTP_PASSWORD}" >> /etc/postfix/sasl_passwd
+    postmap /etc/postfix/sasl_passwd
+  fi
+fi
+
+
 #Start services
 supervisord