[4] Additional hierarchy specific rules (see Breidbart Index) allow cancelbots to send third-party cancels to remove spam.
The body of the Control field contains one mandatory argument, the name of the group to remove.
* removal and creation of groups is handled symmetrically, i.e. an unsigned rmgroup message is used as formalized proposal.
[7] In 1995 the Church of Scientology attempted to silence criticism by sending mass "rmgroup" messages to Usenet servers targeting alt.religion.scientology, an example of the church's continuing efforts to suppress material critical of Scientology on the Internet.
Answering control messages with large emails can be exploited for a Denial of service attack.
Thus news servers stopped implementing sendsys long before it was declared obsolete by RFC 5537.
[10] News servers traditionally allow only selected users to send articles with these lines.
The format of "Arpa Internet Text Messages"[11] is the common base for Usenet[12] and E-mail.
For control message a special format is required since the essential information is in the header fields.
Most news servers are configured to both automatically execute controls signed with the right key and ignore anything else.
Cancel-lock[clarification needed] is much simpler, but neither commonly accepted, nor implemented in popular news servers and newsreaders.