On Mon, 24 Feb 1992, Tom Cervenka <CTCT100@UICVMC> wrote:
> I want to restrict certain non-RFC compliant or otherwise chatty mail
> systems from bouncing mail to my list. If I add a subscription for the system
> and set its options to NOMAIL, will this prevent LISTSERV from accepting
> posts from the mail system?
>
No.  It will only prevent LISTSERV from sending a copy of a posting to that ID.
 
What the LISTSERV-manager(!) at a node can do is issue:
 
! SERVE        user OFF                     Permanently suspend access from
!                                           an abusive user or gateway
!                                           (restore with 'SERVE user')
!
Any non-privileged user can "undo" this (if they know it exists) by issuing:
 
! SERVE     userid@node
!
!   Returns service to a disabled user. To prevent loops and 'message wars'
!   to occur, LISTSERV will automatically  "disable" a user after receiving
!   10 invalid commands from him. Further commands will be completely ignored
!   without any error message being  sent back, until service is restored
!   from another userid/account by means of the SERVE command.
!