"LISTSERV list owners' forum" <[log in to unmask]> wrote on 
04/24/2006 01:51:12 PM:

> It appears that Verizon made some changes to their spam policy this 
> weekend. Verizon subscribers were dropped from all of our hosted lists. 
> Anyone else experiencing this?
> 
> >   Last error was: 5.0.0 550 Email from your Email Service Provider is 
> > currently
> >                   blocked by Verizon Online's anti-spam system. The 
> > email
> >                   "sender" or Email Service Provider may visit
> >                   http://www.verizon.net/whitelist and request 
> > removal of the
> >                   block.

Any indication what landed your server on their block list?  Did you get 
reported by a subscriber or was it simply due to volume?