You might check the Daily-Threshold= parameter for the list.  The
default number is 50 messages per day.  When this is exceeded, the list
is held and the list owner must issue a FREE command.  For reference,
this is in the Distribution Keywords section of App A of the List
Owner's Manual for 1.8b.  This should clear up after 24 hours and then
reoccur when the volume is again exceeded.
 
If it is only occuring on one list or the list is not freed when you
FREE it, you might want to ensure that storage resources associated
with that list are not full.
 
You wrote:
>
>I am sorry if this is silly question to post on this mailing list.
>But I could not find the solution in my "List Owner's Manual".
>One of our list we manage starts sending "xxxx-l list is held"
>message to subscribers whenever they  post article on the mailing
list.
> . . .
>Taeko Thompson
>