docuent that ->messages is a one-shot deal
Backends for ...
rmail
http://quimby.gnus.org/notes/BABYL
mh
http://www.ics.uci.edu/~mh/book/overall/lin.htm
emaul? (probably not)
http://search.cpan.org/author/KJOHNSON/MailFolder/Mail/Folder/Emaul.pm
and
mboxo mboxrd mboxcl and mboxcl2
(only mboxcl2 needs special stuff?)
Possibly
Eudora (mbox variant)
Outlook Express
Outlook (dbx)
Outlook2000 (mbx)
http://mbx2mbox.sourceforge.net/