I have the same unresolved issue described here:
I have the primary iCloud/Junk folder featuring the “x” mailbox icon. I also have an iCloud/Junk folder that features a standard folder icon. Every day about 90% of my Junk mail goes to the plain folder icon iCloud/Junk folder instead of the primary “x” icon folder.
Interestingly when I log into iCloud mail via a browser the “x” icon Junk folder there matches the contents and number of emails as the plain folder icon iCloud/Junk folder on my mac.
On my mac, the right click “Erase Junk Mail” command only erases mail in the “x” icon Junk folder. If I highlight the mail in the plain folder icon Junk folder and choose “Message / SpamSieve - Train as Spam” it is migrated to the “x” icon Junk folder where I can erase it.
If I delete the plain folder iCloud/Junk folder it is simply recreated when new junk mail arrives.
In the Accounts/Mailbox Behaviors tab I’ve ensured that I’ve selected the “x” icon iCloud/Junk mail folder from the drop down menu (both are visible here too).
Any ideas or suggestions for removing the plain folder iCloud/Junk mailbox and mapping all junk mail to the more capable “x” icon iCloud/Junk mailbox?
I’m using SpamSieve 2.9.52 with Apple Mail’s “Junk Mail Behaviors” tab disabled.
I’m running a MacBook Pro (15-inch, 2016) with Big Sur 11.7.6.