If you're like me, you've been emailing "like it's goin' outta style - since '95". If that's the case, you probably have ~100,000 emails saved up in various locations, and if you've had internet since 1995 then you also probably are now (like me) addicted to Gmail and figure it is likely the only email system you'll expect to be using for the next 5 or 10 years. It's also got a massive 10Gb archive space on it, and a little note at the bottom of the screen to the effect of "You are using only 7% of your allotted 8Gb of storage space on Gmail", that is just tempting you to dump a pile of emails in there.
So I finally took the plunge, and it wasn't that tough (albeit a few small annoyances):
- Make a label or labels in Gmail which will translated into a folder in Thunderbird.
- Add gmail as a new IMAP account to your old Thunderbird or Eudora client.
- Then just drag, drop, and wait while the magic happens!! It's great. Emails are auto folded into gmail threads... Amazing.
- I saw this message come up a lot: "Unable to append message to folder". This is either because one of the emails in your list is not compatible with Gmail, or you are overloading Gmail's bandwidth with all your flirty teenage emails from 1994. Or both. Anyway, to fix it I just deleted any offending emails as they went, and tried to shorten the list of emails I was transferring in 1 go to more like 60-100 emails, rather than the whole folder of 9,000.
- Note that if you get the above error Thunderbird will stop transferring the remaining emails (crap). This sucks if you're trying to copy the whole lot of them overnight, so you'll probably need to have your old laptop set up beside your big new computer and keep a roughly keen eye on it all afternoon and evening (that's what I've been doing). Re-starting it on smaller-sized lists is a pain, but it seems to work eventually.
- Note that it looks like you're getting multiple copies of emails if the above happens. Turns out that I am pretty darn sure that Gmail is actually auto-deleting duplicates for you!! This is AMAZING. So any bad server things and Gmail seems to handle it quite gracefully, so that rocks. I thought I was going to have to download some Thunderbird "find duplicate emails" plugin and run that beast on my Gmail IMAP folder, but seems like it's all good.
Good luck! And happy re-discovering of all your old email threads and old friends. :)