We support a list which hits its daily-threshold ( 150 ) constantly.
 
When additional messages arrive, sender gets a message that they are Held.
 
1) WHERE/How are they stored ?
 
2) Is there a limit to how many message can/will be held ?
 
3) can I query the number of held messages for a list ?
 
( I have queries from people who claim 3-week+ delay - unfortunately
  we do not ( understandably ) maintain notebooks on that particular
  list so I cannot easily dispute their claims )
 
-mike