Thank you @JeffL for your time.
I used to be Unix (Solaris, remember?) and Linux administrator and shell scripting (or “dinosaur” languages like Perl) is nothing new for me - of course cron as well 
The whole idea came to picture when I completely accidentally deleted 1 folder on my Mac from my email - I used Apple Mail client - I had everything on my Time Machine but… bloody Apple Mail client does NOT have any config option to keep always full messages on local comp - only headers. So of course Time Machine had all my Sent folders/messages but not all incoming ones.
Then I called ISP and asked for restore from backup - these guys told me: “only last 24h” - omg!
So Thunderbird came to help as I can easily set up “download full messages to local comp” - but then this has to backed up (using odrive).
Ok, I will think further - there is no “boxed” solution I see so I will need to think further what to do.
1- If I keep syncing in real time without versioning my “accidental” deletion of the folder will be immediately synced to cloud as well so in such case the whole idea of backup of my mails will go to trash ;-(
2- if I stay with versioning, the moment I will have to restore it and some folders will have 200 versions - I will die as well
But probably the second option is the only possible with extra - from time to time - deletion of all “older than…” files from the backup - but this has to be done on cloud side… any option for this in odrive “backup to odrive” solution? RETENTION POLICY I am thinking about
My way of coping with emails is: ALWAYS Inbox must be empty - all messages are distributed into the specific folders so truth be told my Inbox is always… ZERO bytes So the backup must go through all folders in mail program - copying specific folders to one place is not possible - I have probably 100+ folders in my email and some messages are from… 2003 - yeap, don’t ask me why I need them but…
Anyway, thanks again for your help.