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I'm planning to do some backups of my e-mails in my yahoo account.

I'm afraid to do it using Outlook or Thunderbird, and be "locked" to their formats. I know Thunderbird is Open Source, but I don't know if it's format specification is a standard one, and just because it's open source doesn't mean it would be easy to recover data in the future.

Does exist a standard format specification to e-mails downloaded from POP3 accounts, that I would be able to read/open without specifically opening the e-mails accounts?

Each file would be an e-mail, with metadata as data received, attachments, and such.

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up vote 5 down vote accepted

Thunderbird's local mail stores are in the standard mbox mail format.

Another option is to back it up to another mail provider (e.g. Gmail, your ISP, etc.). That way your backup is accessible via any mail client. You could have Gmail automatically POP mail, or you could use an IMAP synchronization tool, or some other method to transfer the mail.

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+1 for mentioning that about Thunderbird, and here's a reference: I second the suggestion (which everybody has made, I guess) that mbox format is the way to go because it's the closest thing to a standard email storage format. – David Z Jun 24 '10 at 18:07

There is a standard format called Unix mbox format. I'm not sure whether Yahoo Mail can export to mbox format.

That said, Outlook is used by zillions of people and has been for years, so if your email is in PST format, you can feel pretty confident that you'll always be able to find tools to extract it.

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I'm not a free software Zealot, I use Windows and Linux at home. But I've been a little concerned about storing things in proprietary formats. My father has some really old documents that were written using an application called "Type Script" in MS-DOS almost 20 years a go, and I can't open them anymore. I don't want to have the same problems. If there is the mbox format, at least I can try to search for an email client that possibly converts the emails from my account into this format. Thanks! – Somebody still uses you MS-DOS Jun 24 '10 at 17:23
FWIW, there's not a lot to mbox format. Your mailbox is basically just a text file consisting of concatenated messages. Each one starts with the string "From ". You could read it perfectly well in less, Notepad, etc. – coneslayer Jun 24 '10 at 17:31

Mbox format is a simple text file, so even with a text editor you can see your emails. Well... you will need HTML viewer if you have receive email in html and some decoders to recover the attachments. But until the actual emails standards still the same, you always have some tools to decode the files.

PST can have tons of applications, but it isn't a simple text file.

About POP3, is just a protocol for your email client communicate with the server, and can be also IMAP or MAPI (in case of exchange servers). How the mail client saves the email is what we told you before. Thunderbird use mbox (like some unix email servers), PST in case of Outlook, and even Evolution have some other formats besides mbox, including have a single file per message.

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The "one message per file" method is often called Maildir. – afrazier Jun 24 '10 at 20:50

i would use 'getmail' to retrieve the mail periodically into either 'mbox' or (preferable) 'maildir' storage. maildir is preferable because each mail is a plain textfile.

(getmail on windows works best from within cygwin)

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