Specifies a password needed to post to the list.
The presence of this attribute forces a reprocessing pass. As the message is enqueued to the reprocessing channel, the password is taken from the header and placed in the envelope. Then, while reprocessing, the password is taken from the envelope and checked against this attribute. Only passwords that are actually used are removed from the header field.
This allows for routing to the moderator in the event of a password failure.
LDAP_AUTH_PASSWORD is the MTA option used to specify a different attribute name for this function.