[This is from
http://athensfbc.com/pipermail/imap-tools_athensfbc.com/2013-May/000211.html]
The question sometimes arises: I exported lots of messages from an IMAP server using the IMAP Tools. How can I import them into my local Thunderbird folders?
There is a free plugin for Thunderbird which makes this easy to do. See
https://freeshell.de//~kaosmos/mboximport-en.html. The plugin can be downloaded from:
https://freeshell.de/~kaosmos/index-en.html.
1.) Download the ImportExportTools-2.8.0.2.xpi plugin.
2.) Install the plugin. Go to Tools --> Addons (or Extensions). Click on "Install", and select the ImportExport xpi file.
3.) Restart Thunderbird
4.) Go to Tools --> ImportExportTools
5.) If you exported the messages using
MboxtoIMAP then select "Import mbox file" and "Import one or more mbox file", select the file(s), and click "OK".
6.) If you exported the messages as individual files using
imapdump.pl then select "Import all messages from a directory", select the directory, and click "OK".
The plugin works with any .eml files, that is individual messages in RFC822 format, or a file of messages in Mbox format.
-Rick