Mapping over Zmail to/from headers

[Jeffrey Mark Siskind <Qobi@zermatt.lcs.mit.edu>]

I have a question which perhaps someone can offer a simple
answer to.  I would like to make a list of all email address
with whom I have communicated.  Accordingly I would like
to map over my babyl file and produce a list of all
net addresses appearing in either "from" or "to" fields
appearing in the header.  Does anyone know of functions
in zwei that would make this task (of parsing babyl files
and headers) easier?
        Thanks,
        Jeff