My department is being forced by the university administrative IT unit 
to MS Office365 distributed server ("cloud") email service, as I have 
communicated in a previous query.  We are now being advised by others 
who have been forced to do this -- but of course not by IT -- to backup 
all of our email.  I use Mozilla Thunderbird, incoming IMAP, outgoing to 
a designated SMTP server.   I have found

http://www.beyondinbox.com/beyondinbox-download.html

licensed for fee that claims to function under Linux, MacOS X, and MS 
Windows for this purpose.  There are concerns to find a viable 
licensed-for-free product that will copy IMAP folders and all of the 
contents thereof to a local harddrive directory/file structure and that 
can restore these same IMAP folders and the contents thereof back to a 
remote IMAP service -- thus guarding against loss -- up to the last 
backup snapshot -- of all email.

Has anyone any experience with the above application?  is there a 
licensed for free reliable, viable alternative, GUI preferred, for Linux?

Yasha Karant