Dave,

You need to use an imap server, I do not know if gmail has this or not, as pop (IIRC) does not allow you to grab headers and download / leave on the server.

If I am wrong please do not shoot me, as I am not 100% sure, but have always set users up with imap when they have asked for this feature.

Eudora can do it, somewhat skankily :)

My usual solution is to designate one machine as the 'canonical' machine tha I want the full archive of my mail to turn up on eventually. This machine is set to download immediately.

The other machine I set to leave mail on server. I quit each mail client when I'm finished using it at that location.

Works for me, but that's with Eudora, don't know how well it'd work with Mail.app

Have fun,
Shay
--
=========================== Shay  Telfer ================================
 Perth, Western Australia   Technomancer  Join Team Sungroper in the
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 http://public.xdi.org/=Shay    fnord     <http://sungroper.asn.au/>