I've been using Ubuntu on several machines for a while (it all started with my
now retired Ubuntu server 6.10) and I have used both Evolution and Thunderbird
in the past. However I have always had my master copy of email on XP / Outlook &
archived each year to a new pst file, which I then backup onto DVD (the copy on
the PC is then left unmounted and moved to a folder that I exclude from my daily
back up).

I now want to move my email onto Ubuntu and I need a way to manage archives of
old email. I have these concerns:

1. I know that access to existing pst files is not too much of a problem in just
about any email program, as they can all import a pst file. However it would be
much easier if I could open a pst file, and when I've finished to close &
unmount it again as I can in Outlook. This would be quicker than import & then
delete each time.

2. I would like a way to archive email each year into a single file or folder
that I can backup to a DVD. However the difficult part is that this really needs
to be:
a) an export, so I can manage the size of dayly backups for live data
b) something I can easily mount when needed and unmount when I've finished with
it (as with my pst concern above)
c) in a common or standard format that is compatible with a wide range of other
email programmes to protect me from loss of access to archived emails if
development on any single email program stops.

To best achieve these aims, would you recommend Evolution, Thunderbird,
something else, and with which add-ins or features?