thunderbird android backup emails to mbox

i know that thunderbird for android works differently than desktop version, that's ok. i ask here to add to thunderbird-android function of backup emails to mbox-file, collect emails from selected server and make backup in mbox file which can than be opened in thunderbird-desktop. i must emphasize, i don't ask that thunderbird-android should be capable of handling mbox-files, this would be pure backup functionality.