How do I transfer a large number of emails from Outlook to Thunderbird?

November 1, 2004 5:43 AM

Thunderbird forcefeeding (mi)

I want to switch from MS Outlook to Thunderbird, but I want to take my 20 000 + emails with me. Every time I try to import them, Thunderbird freezes, possibly because I have too many subfolders and too many mails (yes, I know). Now MS Outlook has a possibility to export all those mails into a nice .pst file, which you can then download into another copy of MS Outlook – but not into Thunderbird. This bird only accepts imports from other programs, and not from folders or files. Is there any way I can bypass this? Asking this question on the mozilla newsgroup didn’t get me any answers, so I’ve put my hope in the whizzez of MeFi.

posted by NekulturnY to computers & internet (11 answers total)

I've only done this one, and it's been a while, but I'm pretty sure that Thunderbird doesn't import mail directly from the PST files, but somehow hooks into a running copy of Outlook to do the import, so it's possible the problem is on the Outlook end.

How large is the PST file? The practical limit is 2GB, so if your file is larger this could be a problem.

If all of your mail is currently in a single folder, you might try to break it into separate folders. If this doesn't work, copy your mail from one PST into multiple PST archive files (maybe broken out by year), connect them to outlook one at a time then do your import.

Before you try any of this, make a backup copy of your PST file, since it's terribly easy to corrupt this file. < /voice_of_experience>
posted by SteveInMaine at 6:06 AM on November 1, 2004

I've only done this once.

And sheesh, talk about your run on sentences! Time to throttle back on the caffeine.
posted by SteveInMaine at 6:07 AM on November 1, 2004

I'm pretty sure that Thunderbird doesn't import mail directly from the PST files, but somehow hooks into a running copy of Outlook to do the import.

Exactly. That's what I meant with my overlong blabla: it's impossible to import a .pst file, because Thunderbird wants to pass through Outlook to get the mail.

So what you're saying is: break up the PST files, import them to Outlook one by one, and then import them to Thunderbird one by one? I guess that's a possibility, but it would certainly be a huge undertaking.
posted by NekulturnY at 6:09 AM on November 1, 2004

Outlook's pst files are an example of what Microsoft calls a "structured storage file". It's basically a little file system, with metadata, within a standard binary file. (It's actually a bit more than that in this case, I think, because of the optional access control and encryption built into pst files. But don't take my word on it that this is unique to the pst files.) The Office suite apps all use this file format. It's undocumented and subject to change. This is why almost all Outlook pst import/export tools, standalone or part of another app, just hook into the API to do their work.

I went on a long online trek looking for an app that can read pst data natively. The very few that I found are all relatively expensive, especially for a one-time use.

I use "ArchivER", which I bought a few years ago, to export from Outlook (using the API, not reading the file natively) my mail to various formats. It's not a very flexible tool—but none of them I've tried seem to be. It, and others I think, when exporting messages to, say, text or html or rtf, relies upon Outlook's presentation of the message in that format (which does not include all the headers) and, worse, if it came in that format in the first place. However, the native Outlook msg format, which is also a ssf format, contains all the message's data. So what I've done is use ArchivER to expert all my mail to individual msg files. Then, last month, using a Perl module that someone wrote that valiantly tries to understand structured storage files, I wrote a Perl app that takes all these msg format messages and writes them into one big standard UNIX mailbox file...which is far more portable and all the headers (I think) are preserved.

I mention all this as it might help you. Feel free to email me if you like. And hopefully this answer will be helpful to others trying to solve these sorts of problems.
posted by Ethereal Bligh at 6:32 AM on November 1, 2004

I think I've read that if you export all your mail from Outlook into whatever format can be read by Eudora, that format can then be imported into Thunderbird.

sorry for no links but I can't remember where this was...probably in the tb forum somewhere. can anyone confirm this?
posted by jacobsee at 8:30 AM on November 1, 2004

Sounds good, but what about the 2 GB limit, jacobsee?
posted by NekulturnY at 8:52 AM on November 1, 2004

I don't have Outlook and don't know anything about it. You might search the TB forums. Looks like TB and Eudora both use the "mbox" format. Does Outlook have any mail export options?
posted by jacobsee at 9:17 AM on November 1, 2004

no help really (sorry), but if you've got a lot of email you might be better moving to a mail client that uses the maildir format (not thunderbird, unfortunately).
posted by andrew cooke at 9:41 AM on November 1, 2004

mmkay, andrew, sounds interesting. More info? Suggested mail clients?
posted by NekulturnY at 10:21 AM on November 1, 2004

If you drag-and-drop e-mails from Outlook to a directory on your disk, Outlook will export each individual mail as a .eml file. I don't know if that helps for importing them to Thunderbird, but I've had problems with corrupted .pst files in the past and find .eml to be a much better way to back up my e-mail.
posted by fuzz at 3:53 AM on November 2, 2004

Outlook Express will save those emails as ".eml" files, but Outlook will save them as ".msg" files. Some other mail apps can read ".eml" files natively—they're not structured data files—but don't understand ".msg" files natively.
posted by Ethereal Bligh at 7:14 AM on November 2, 2004