I have discovered, from a list subscriber, that the listserv running
Z3950IW supports the digest feature.  If you turn this feature on, then
you will get a single posting containing all of the email from the
Z3950IW list instead of a posting for each message.  The digest is sent
daily.  This reduces the amount of email that you get but you lose
the immediateness (sic?) of individual postings.

If you are interested in turning this feature on, send an email to
LISTSERV@NERVM.NERDC.UFL.EDU with the single line of:
                SET Z3950IW DIGEST

If you decide to go back to individual postings, send an email to
LISTSERV@NERVM.NERDC.UFL.EDU with the single line of:
                SET Z3950IW NODIGEST

Have fun,
markh