thanks, got it, so TorBirdy makes the trick.
Another issue is, how to deal with the folder and files that contain the emails? I mean, e.g. in Thunderbird under Windows, there is a “Local folder” folder, with .msf files and other files without extensions. They contain the emails.
In Whonix, will there be such file(s)? How to store them safely and securely? If an adversary forces to open Whonix and Icedove, then emails are there.
I was wondering whether it is possible to e.g. making a Truecrypt container on host, which would be a shared folder in Whonix WS. Then this container would have the Icedove file with emails. If the Truecrypt container is not opened when booting WS, then file would remain encrypted and Icedove could show nothing.
Any better way for managing Icedove ‘email file’?
(This would be a solution for my other concern: if I just keep the emails in Icedove, then everything is stored in the vmdk file in VM VirtualBox. If I have to reinstall host or VirtualBox, then I’m not sure if simply backing up and restoring the vmdk file would work; otherwise I lose everything which was inside Whonix).