ezmlm automatically detects are rejects messages that are sent from other ezmlm mailing lists. Some other mailing list managers do not use a rigorous mechanisms to verify subscribers. Thus, it is possible to subscribe an ezmlm list address to such a mailing list. You can easily block such a list by adding the address to the ‘deny’ if you use the ezmlm-make(1) -k option. However, you can also configure ezmlm-reject(1) to reject messages based on specific headers placed into DIR/headerreject. A set of headers which will catch mailing list managers known to us are listed in the ezmlm-reject(1) man page. To activate this option, you must specify the -h switch and DIR on the ezmlm-reject(1) line in DIR/editor. Naturally, you can make this the default by editing ezmlmrc(5) (see Customizing ezmlm-make operation).