I'm looking for a program that backs up all my emails from an online Emailaccount that support POP or IMAP by saving them as plain text files (an open document format or pdf file would also work) . Ideally in the following way:

1) Every email should be in a folder whose name is the subject of that email.

2) The email inside that folder should be saved in text (or at least in an different open document format or pdf file)

3) As a plus, all attachements of an email should also be stored in the corresponding folder

But it's still ok if it is, for example, just one long text file.

I've tried evolution and thunderbird and couldn't find such functionality (please notice, that I'm not a regular user of these programs since I manage my email online, so I barely know my way around them and only tried them out for the purpose of making this backup).

This program doesn't have to have email sending functionality and all the other stuff that evolution & thunderbird can do. I just need to archive my emails, so it only would have to download them and organize them in some way. Saving my attachments would also be nice.

The reason I'm insisting on *.txt (or open document format or pdf) files is that I want to be able to read my emails in 10 years from now. If my emails are stored in some format of thunderbird for example and with some update of it support of that format gets dropped, I'm lost. The *.txt probably will still be readable in 10 years time. And open document format files - while there may not be a program that supports them in 10 years - are still readable with a txt-editor, so I can use that to read them and extract the email from all the header data. For PDFs I assume there will still be a reader in 10 years.