If a person was served off by LISTSERV we would receive an email notifying us.  It
would say something like "[log in to unmask] has been served off after 50 unsuccessful
commands".  I forgot if that message went to the list owner, or just the LISTSERV
Postmasters.

> Sending too many incorrect commands (either explicitly by the user, or
> implicitly by some errant mail process) to LISTSERV itself can cause
> this.
>
> You as another LISTSERV user can try to issue the following
>
> SERVE userid@node
>
> If that returns service, then it was probably the above problem. If
> not, the a LISTSERV admin explicitly had turned OFF service and you'll
> need to contact that admin.
>
> /Pete