set default value for POSTFIX_STRIP_SENDER_HEADER env

Author: crazy-max

rootfs/etc/cont-init.d/00-env

@@ -83,6 +83,7 @@ MAIL_ENCRYPTION=${MAIL_ENCRYPTION:-null}
 
 POSTFIX_DEBUG=${POSTFIX_DEBUG:-false}
 POSTFIX_MESSAGE_SIZE_LIMIT=${POSTFIX_MESSAGE_SIZE_LIMIT:-26214400}
+POSTFIX_STRIP_SENDER_HEADER=${POSTFIX_STRIP_SENDER_HEADER:-false}
 POSTFIX_SMTPD_TLS=${POSTFIX_SMTPD_TLS:-false}
 POSTFIX_SMTP_TLS=${POSTFIX_SMTP_TLS:-false}
 POSTFIX_RELAYHOST_AUTH_ENABLE=${POSTFIX_RELAYHOST_AUTH_ENABLE:-false}