My idea is check senders (MTA s) ip and priviledges to use smtp, not using protocol headers or other content filtering method. My idea is control connection (ip) using reverse dns lookup database, not dns lookup. My proposal include also method to handle roaming mta. Mail sending is done from ip, not from domain. Reverse dns is mostly controlled by operators and "big companies", so we have less players as in domain structure and I believe that it is easier to make "operator blacklist" as domains. This idea is simple (too simple to be true ? That I m asking) to add every access control level : firewall, proxies, filters, wrappers, smtp servers, ... Proposal rMX using rDNS: http://www.awot.fi/sf/browser/showfile?cust=awkoulutus&subdir=dns&doc=reverse_mx I m waiting feedback, have I missed something ? -jukka- Jukka do.t Inkeri at Awot do.t Fi