There is a constant increase in the traffic load between RFC822/SMTP and X.400 mail protocols, thus new and easy to use interconnection tools are required. In particular, the duplication and decentralization of gateways between the above protocols requires that they should be usable also by non-experts. The new gateways should be maintenance free. One of the major problem is RFC1327 mapping table maintenance. A mechanism for automatic distribution of mapping rules by means of Internet Domain Name System (DNS) has been implemented and tested; the positive results are presented here. In particular, we specified an Application Programming Interface (API) and developed a library which allows a gateway to interact with DNS in order to obtain mapping rules, without the need of statical tables. Using these basic tools, we developed also a new RFC 1327 gateway which does not require local maintenance. This new gateway was distributed over our INFNet backbone, resulting in an efficient and fault tolerant two protocol (X.400 and RFC 822/SMTP) E-mail distribution backbone.