I ran the Thunderbird add-on, "Attachment Extractor" (http://www.eviljeff.com/?page=moz-extensions) and (https://addons.mozilla.org/en-US/thunderbird/addon/attachmentextractor/) against 5,174 messages in my IMAP inbox.
- Extract the file attachments from my messages to a local folder.
- Utilize the option to keep a text (HTML) copy of the message itself, as a file, in addition to the extracted file attachment.
- Delete the file attachments, after downloading them from the email messages, while retaining the email messages themselves.
- Thunderbird 8.0
- Windows 7
- Extraction folder set to a local drive
I found the tool to be useful. I particularly liked the ability to include variable keys to include in the resulting file names.
The first time I ran the utility I opted to use the 'Save message txt to file' option. Doing so created a separate HTML file for every message in my inbox. While an interesting backup, I found no real use for the HTML files, so I aborted the process, disabled that option, and simply downloaded the attachments themselves.
For my UWM account I chose 'Delete the attachment from the message' and its 'Delete with AE's internal (experimental) routine. This method allowed me to bypass having to okay the deletion of each message's attachments. Again, just like using the tool itself, the risk of utilizing that option is your choice.
Once you download your file attachments, make sure to back them up to an external drive, a cloud drive, etc., using the desired encryption technique of your choice. I suggest TrueCrypt, to encrypt containers, or Crypt4Free to encrypt individual files. Both are free and easily locatable via your favorite search engine.