I finally got sick of all the problems with Outlook, bit the bullet and transferred all my historical email online. Having spent a few days using "native" Gmail (vs. POP to Outlook) I already feel a lot more productive.
Ironically I'm writing this on the very day when Yahoo announced unlimited storage - but I'm with Mike on this: message threading, labels and powerful search still make Gmail (the Google Apps flavor) the best choice for me. At least for now - but I keep an eye for the next incarnation of another product - will name it in due course (if you guessed which one, you're probably right ).
Migrating to a new email service wouldn't be complete if you couldn't move all your old "baggage" with you. Apparently this is a burning problem for many, as a year-old post I wrote on the subject is one of my most popular hits ever. Back then I was still happily (?) POP-ing it down to Outlook, but wanted a fast all-in-one searchable archive, and Gmail was the perfect solution. But none of the solutions were perfect - until now.
There are several "gmail-loader" tools on the Net, but some simply don't work, others change the original sender information to the email account they use for the transfer - pretty bad, IMHO. My simple solution a year ago was using Thunderbird with a redirect extension. You can read the steps to achieve this here. Even this solution wasn't flawless: gmail listed all historical mail with the date of the transfer - the original date was sill preserved and searchable, you just got the list display messed up. This still appears to be the biggest hurdle users face according to this new discussion on Lifehacker.
The final solution comes from Google themselves: now that they quietly expanded Mail Fetcher to Google Apps accounts, and removed the "non-gmail source" restriction, there is a simple yet perfect two-steps process to get it all done. Gmail Mail Fetcher fixes the date problem, so now in two steps and using two email accounts you can get it all right.
Step 1:
Load all your client-based email to a temporary Gmail account either using my Thunderbird procedure, or, for an easier and elegant solution, get hold of an IMAP account.
Gmail does not support IMAP, but my old provider, 1and1.com is not a bad choice: 5 email accounts, 2G each with IMAP support $0.99 / month. In Outlook (or whatever email client) set up an IMAP account according to the instructions from your online provider. Then folder by folder copy all email into the Inbox on the newly created IMAP account. Don't forget your Sent Mail folder: yes, that goes into the IMAP Inbox, too. Open all your archives and repeat the same process.
Don't worry if it takes a wile: Outlook doesn't simply copy between local folders, it shoots up all your email to your temporary IMAP server on the web, and you'll be constrained by your upstream speed (typically lower than downstream). If you have a spare PC, it's a good idea to use that one.
Step 2:
Now that your email is online, make sure POP access is enabled from your temporary account. If this is a gmail account (not IMAP), this is the setting you need:
"Enable POP for all mail (even mail that's already been downloaded)"
Then in your Gmail target account - the final destination where you want to have all your archive mail - set up Gmail Mail Fetcher to pick up all mail from your temporary account. The dates will magically be fixed! Here are Google's instructions on setting up Mail Fetcher. Do NOT check the button for "Leave a copy of retrieved messages on the server" - you do want Mail Fetcher to "eat" them all from the temporary account, in fact that will be one of your indicators that the transfer is finished.
Be prepared for a slow process - Gmail will poll your temporary account at 60-90 minute intervals, fetching 200 emails at a time. At Settings > Accounts you can follow the progress, but ignore the "nnn mails remaining" indicator, as it's totally wrong. When all done, don't be alarmed that the number of fetched emails is less than what you started with: your email client (and the IMAP server) counted individual emails, while Gmail will group them into thread, and reports the thread count, which could be significantly lower.
Last, but not least a word on labels / categories: if you nicely organized your Outlook archive in folders, Gmail has no way to preserve that structure. The trick here is to do Steps 1 and 2 in iterations, completely transferring one folder at a time. Then you can set a label for all your fetched email to match the original Outlook folder, and keep on changing it folder by folder.
Finally there is the issue of backup: after all we heard of disappearing Gmail... If you trust Gmail, just worried about what may happen to your individual account, there is always the option of setting up a shadow-gmail account which will fetch everything from your primary one. If you want a local archive, "just in case", either run Outlook to periodically POP your mail down, or I believe Thunderbird has a plugin that allows it to be minimized to the system tray permanently and check the POP server in the background.
link to original post