Each e-mail address has its own "STATUS" file.
"STATUS" file e-mails are not deletable from the POP mail server unless
specifically commanded to delete them within Thunderbird via a separate
command
or when all "STATUS" files are duplicated based on time stamp.
"STATUS" files are based on changes and store individual e-mails and/or
their marking (New, Deleted, Un-read)
The frequency of generating time stamped "STATUS" files is based on file
size of STATUS file.
"STATUS" file e-mail may only be transmitted with PGP or some form of
encryption.
"STATUS" files are created chronologically, each access adds to the
stack to be sent between Thunderbird 1, 2, 3...N
The checking of "STATUS" file happens within Thunderbird
Thunderbird 1<---> POP mail server <--> Thunderbird 2
Thunderbird 1 receives e-mail < -- POP mail server
Thunderbird 1 creates "STATUS" file based on changes (New, Deleted, Un-read)
Thunderbird 1 sends "STATUS" file via e-mail in PGP encrypted file --->
POP mail server
POP mail server --> Thunderbird 2 receives e-mail including PGP
encrypted "STATUS" file
Thunderbird 2 says "You have received a "STATUS", Processing "STATUS"
file now.
Thunderbird 3 added and receives "STATUS" file e-mail < -- POP mail server
Thunderbird 3says "You have received a "STATUS", Processing "STATUS"
file now.
Thunderbird 3 sends "STATUS" file via e-mail in PGP encrypted file --->
POP mail server
I didn't say it was easy, but it is possible.
Think of it as a very unique and fancy Message filter.