I have no idea whether Listserv changes its IP address, though it 
sounds nuts to me: but we had McAfee here for some years and never had 
the slightest trouble.  If this is a school address, it's the network 
administrator's responsibility to maintain the staff's access to 
listservs. I recently had this problem with another spam filter at a 
university ISP, regarding a list for university teachers I administer, 
and the staff there was told something similar, until they raised hell 
about it.

Go over the network administrator's head: she's not doing her job.

-- Russ

Russell Hunt
Department of English
St. Thomas University
http://www.stu.ca/~hunt/