Thunderbird - can't stop it writing back to system [SOLVED]

[Giselle567]

I have up-to-date Windows 7 Pro (64), Thunderbird 52.6.0 (32), and licensed Sandboxie 5.23.3 (64).
I've been running Thunderbird outside Sandboxie, no problem, and decided to try sandboxing it in it's own separate sandbox
(called "QP" ... I'll also refer to Thunderbird as TB and Sandboxie as SB ...)
1) In SB settings for QP, in Program Start / Forced Programs, I added thunderbird.exe. With the yellow border, I can clearly see TB is running inside QP (and the Control Window shows those files open).
2) While QP/TB is running, I check for the QP sandbox path that virtualizes TB data (C:\Users\Owner\AppData\Roaming\Thunderbird) where I would expect to find the sandboxed data. Wasn't there.
3) I downloaded some email inside SB, close the sandboxed TB, and checked again ... data not there in sandbox path.
4) Next, I opened TB outside SB, and there were my updated emails back in the system! (Without downloading them from the server.)
SB wrote data back to the system without permission (and seemingly on-the-fly).
5) Back in SB QP settings, I turned off Quick and Immediate Recovery, and added the system path (C:\Users\Owner\AppData\Roaming\Thunderbird) for TB data to Forced Folders ... ran TB in SB ... I could see SB running TB in QP ... same result ... no SB path data, and system gets written to.
6) All my other progs behave properly in SB. Am I doing something wrong? Is there an incompatibility with TB?
Thanks,
G.

[Giselle567]

Whoops, stumbled on my problem/solution ...
Under Sandbox settings / Applications / Email Reader, I had Thunderbird checked.
Without reading the heading carefully, I mistakenly thought that was keeping the data INSIDE the sandbox.
Thanks anyway ... maybe this will helps someone with a similar problem.

[Barb@Invincea]

Hello Giselle567,

Glad you found the solution. Here's a thread which contains all the Email setup requirements in one place:
viewtopic.php?p=132327#p132327

Regards,
Barb.-