why not just specify the folder as the junk folder in your account settings.

I'm a mail server sysadmi. I cannot set that special folder as my private spam folder, because it's a special folder directly managed by my mail server for all accounts in the domain... more than 500.

I have my personal spam folder fully operational and perfectly integrated with Thunderbird and cooperating in spam detection.

I share that special admin-folder on my IMAP-account structure because it make easier monitoring mails tagged as spam by users in the domain and getting shorter times in identifying massive phish/viruses mailing not detected by Automated services to take global countermeasures for all users.

As a workaround I'll modify the share method of the folder to read-only (server-side)... this will forbid Thunderbird from marking/moving mails in that folder. But i think that blocking the analysis should be a cleaner approach

Setting the folder read-only doesn't solve because Thunderbird cannot delete from the folder but after scanning the mails puts a copy in my account spam folder starting the loop!

As the server admin, I would simply add an additional account to display the folder hence getting the opportunity to disable junk filtering on the account. I know of no way to exclude a single folder from junk filtering

If you have 500> users you would like to get technical accounts to the minimum.

I know it's a workaround I can take.

As there was a mean to get this till to Rel 31 through the extension above there should be a way built in the Program structure...

https://addons.mozilla.org/en-US/thunderbird/addon/folderflags/

I've no problem to play with config files directly but not enough time to search for the structure inside.