When I first got my Mac I also made a fundamental shift in the way I manage my e-mail; I switched from Outlook to Gmail. Since I made that switch I've been quite happy; not only does Gmail give me IMAP access so I can get to it from within Mac's Mail, I can also get to it from my little Motorola phone and from any web browser on a public terminal. Sure, Gmail's IMAP implementation leaves much to be desired but the tagging model is really great.
Prior to switching to Gmail I used Outlook for many, many years. I went from version to version, carrying my PST file with me all along the way. Since the newer versions of Outlook didn't have a problem with PST files larger than 2GB I didn't even bother to archive my e-mails. I liked that I could search through my entire e-mail history, dating back to 1996, at any time.
Enter the Problem
So what I've been ignoring for a few months now hit me again yesterday when I had to fire up my Windows XP machine to search for an old e-mail that contained an account number I needed. What I really needed to do was get that 4.1GB PST file into a format that my Mac could read easily.
I did a lot of research and finally found a solution: O2M from Little Machines. This is a little Windows application that sells for $10; it will convert your Outlook E-mail into MBOX files, which are simply UUEncoded text files that can easily be read by Mac's Mail program. It will also produce vCard (vcf) files for your contacts and iCal (ics) files for your calendar events.
O2M is easily worth the $10, even though for me it's a one shot deal and then I'm done with it. This program is really, really quirky though. It's likely using Microsoft's MAPI interface to scan through the contents of Outlook, which means that if you have an archived PST file you will need to open it in Outlook before it can be exported.
Keep in mind this is a Windows application, not a Mac application, so have a PC (or Windows VM) with Outlook installed and running in order to perform this conversion.
Warning! UI Hazard Ahead!
If you care at all about well designed user interfaces you will need to wear some protective gear when you fire up this application. The UI looks like something that a Visual Basic newbie put together in 1992 without the aid of any standard UI components or even a fully functioning monitor. Don't believe me?
See the control alignment? The completely random whitespace? See those little, itty-bitty checkboxes? You get to manually select every single one of them. Got lots of folders like I do? Enjoy. Fortunately I was able to select the first one and then stand on the Space bar while it cycled through all of the folders.
In spite of the UI it does indeed work, plowing through my gigantic PST file and dutifully popping out scores of MBOX files that can be consumed by Mail or even simply searched in their native form if need be.
It can take a very long time to run, especially if your PST file is very large like mine. It's something that needs to be casually monitored too because every once in a while it would come across some e-mail and generate an error message about a bad date format and ask whether it should fix the error (Uh, yeah!) or ignore it, or warn me about exporting a digitally signed e-mail.
I ran this on my Windows XP machine with 2GB of RAM and an Intel QX6700 quad core processor. With nothing but Outlook 2007 running it took nearly 4 hours to process my e-mail, extracting 77K messages in 495 folders (now Mailboxes) and 172 Contacts.
Once you're done with the conversion you can select an entire set of folders under the File / Import Mailboxes feature in Mail. It will also take a little while to suck them in, though not nearly as long as it takes to export them from Outlook.
I decided not to import all of my mail though, realizing that large swaths of my messages were really pointless to keep around (most of the old ListServe messages I had are searchable in Google Groups anyway). I now have one less piece of Windows software to depend on.
Yes, I knocked O2M hard on the UI front but it did work fine for me and was well worth the $10 I paid for it. I just wish the Little Machines folks would update the UI on it.