Have you conferred with the administrators of your email domain?  If you see in the log of your originating mail agent (the sendmail machine your LISTSERV(tm) site uses directly) that items were delivered to the destination servers, but the subscribers don't have the items, then it seems to me that your problem(s) is/are with those destination sites and have nothing to do with the list or the operation of your list host.

In my experience, I'd say your mention of "within about 1 hour" is a symptom of trouble in itself.  I run LISTSERV(tm) 1.8d and LSMTP(tm) together on a 300mhz system, and it delivers over 4,700 items in less than seven minutes.  But this delivery rate will be affected by your site's external connectivity... we have "much better than T1" here, though I'm not sure exactly just how fast it really is.

>>> [log in to unmask] 04/08/03 04:19PM >>>
We have a list with about 5100 subscribers.  In two recent e-mailings, I received my copy within about 1 hour of initial delivery (I am listed as one of the owners).  Other subscribers with the same e-mail domain as me are still waiting (now 5 days) since the e-mail went out.  Further, we have yet to confirm that any other subscribers on the list got the e-mail.  The listserv logs and the send mail logs indicate the mail went out to all subscribers.  Is this normal?  Has anyone else experienced long delays in delivering e-mail like this or even mail not getting delivered when the logs say they were delivered?