We currently host our email third party and we're very unhappy with the service so we're bringing it internal. Since my district has an SLA already from ZEN we're going with Groupwise.

Here's my problem..

Many administrators are using Outlook to read their mail.. some have 8+ gigs of saved mail from over the years. Many other users, myself included use Thunderbird to read out mail. Ideally I would like everyone using the same groupwise client after this transition or at least the web client.

I've seen a few free outlook to groupwise converters but none for Thunderbird.
I'm looking for something cheap to get all my user's local mailboxes off their machines and onto the server when we install it. For instance, the union president has 10 years of correspondence that will need uploading...

So yeah.. please advise.. Anything to help is appreciated!!