Hi, Suppose Mr. X, owner of foobarpunks mailing list, wants to kick out Mr. Y, for his obnoxious letters to the mailing list. Mr. X, however, is concerned that Mr. Y would subscribe through some proxy address and would continue replying to messages to foobarpunks. It is assumed that the only person out of the whole universe, Mr. Y, cannot be trusted. The problem is that X does not know which of the subscribers is Mr. Y. The question is, is there a technical way to disable Mr. Y from reading the list, or detect which subscription address is a proxy for Y? If we assume that, at the moment when Y was kicked out, he was not subscribed through any other addresses, the solution becomes simple: for any new subscription request we require a letter of recommendation from some other subscriber. Since other subscribers are presumed to be trustworthy, their recommendations would be sufficient. It is actually being done in some of the mailing lists. The problem becomes more complex when Mr. Y is already presumed to have infiltrated the mailing list, possibly through several proxy addresses. Is there any way to detect/find which if the subscriber is Y? One of the simple-minded solutions is to _mutate_ mailing list messages so that all readers get slightly different copies of mailing list messages for each recipient. (Such mutations may include common misspellings, inserting spaces, etc) If the mailing list bot keeps track of what changes were made in messages to which individual, and if we assume that Mr. Y has to quote significant parts of messages he replies to, finally the variations in messages may be reconciled with variations in quoted parts. Mr. Y is not stupid, and may go as far as comparing letters, received through different proxy addresses, in order to detect "variations" and avoid quoting them. The question is, is there a strategy of making variations and detecting them in quotes to finally catch Mr. Y? - Igor.