Over 10% of all LISTSERV mail goes  to AOL. That's a whole bunch of mail,
all going  to ONE host. If  your list is  on a server that  delivers 200k
messages daily, there  will be some 20k messages a  day waiting for their
turn  to be  sent to  AOL.COM.  While there  is usually  some measure  of
parallelism,  even  with 10  concurrent  deliveries  it's  a pipe  of  2k
deliveries. If  your delivery  system isn't blazing  fast, this  can very
well take several hours.
 
  Eric