I need Dropbox files redistributed between two drives, due to the lack of space.

I contacted the support and received a standard answer:
"Please Rewind back"

I did that...  BUT ... instead of ameliorating
... it completely damaged my Thunderbird Data base...

I lost some FIFTEEN THOUSAND mails ☹

NOTE:
Thunderbird host business/private mails from 1995 in separated mails-folder

but but but . I solved it . but but but

Some a chanced event  happened ... LUCKY ME ...
 my SSD Laptop Disk USB containing Dropbox Folder,
got physically disconnected mid-July without me perceiving it!!!!

When I discovered that  I jumped table high happy and that happened two days ago
SO ... I proceeded this way.

The SSD disk stayed not connected to the Laptop,
but I connected it to BKP-PC USB
>>>because here it's not actively seen by Dropbox's BKP-PC  

Operating from BKP-PC:

> This way I was able to copy OLD LAPTOP  **/Dropbox/Thunderbird under BKP Backup folders 😇

* Copy BKP-PC Current **/Dropbox/  >in BKP Thunderbird disks
* Deleted Current **/Dropbox/Thunderbird  completely cleaning it!!!

Operating from MAIN-PC:
When Later ..  I booted Main-PC and left it working I discovered that after 10 minutes
!!  **/Dropbox/Thunderbird folder WAS not emptied by Dropbox !!!!

Unheartened ... I resolved to act manually:
So I deleted also from MAIN-PC Dropbox: Completely Cleaning _Thunderbird Folder 😰

Then ... connecting via USB the Laptop SSD to Main-PC ...
I was sure Dropbox dont see it also here and coudnt mangle it ..
 From it I copied all _Thunderbird contents into Dropbox Main-PC folder.

After giving it 20 minutes to complete the Dropbox Syncs,
I started Thunderbird..
... and HAPPILY  ALL FOLDERS AND ALL MY OLD E-MAILS WHERE THERE!

Thanks to my luck, while all old mails archives was recovered, 
Dropbox still garbled the situation :-(

These one in red are not part of the LAPTOP-PC Archives :-(

... and Main-PC [T24] Dropbox Thunderbird's folders should have nothing inside remaining after being completely cleaned.

As you see it seems T24 conflicted with itself !! [ MAIN-PC =T24=TwenyFour ]

______________________OK_________BUT__________________

WHY I'M WRITING HERE?
JUST TO COMPLAINS ?

 N O !

Because:
being unable to use my e-mails System,  I was not able to comunicate with the ticket people!!!

SO THEY CLOSED THAT TICKET !!!
 
BUT  I have to tell them:
The issues are all on the DROPBOX SIDE
...and even REWIND KEEP GARBLING THE ISSUE.

Lucky I was to have an unexpected backup of few weeks.

Last "official backup" was from January, and that would have meant:
 I can recover older mails, and thunderbird would download subsequent mails
BUT
definitively loosing ALL THE SENT MAILS IN THAT PERIOD!!! 

>>LESSON LEARNED<<

A) DO NOT THRUST DROPBOX

B) Restart doing a LOCAL BKP  D A I L Y  ... OLD METHOD

C) ... as you where doing before paying 200€ per year.

If you can /may  please send this as a follow-up to the Ticket-support People!!