If most of those messages are expected not to be junk, why not just change it to 'Filter before Junk Classification'?

Thanks. I'll try that change. But still not sure why: "If Sender = X, move to Y Folder"... should result in a Junk classification. No other Filter has that issue.

Since your filter runs after junk detection, emails are already marked as Junk before moving. Try these:

1. Set the filter to run before junk classification (if possible).

1. Add those senders to your safe sender list to stop them being marked as Junk.

1. Make sure your filter includes “Set Junk Status to Not Junk.”

Hope this helps!

Cheers Sanjay... 1) I had already changed the Junk Classification to: Before Moving 2) There is no Safe Senders list in Thunderbird but I've ensured that all received email addresses are in my Address Book and the Junk setting says to Ignore [Junking] those in my Address Book 3) I had already set the "Set Junk Status to Not Junk" within the Filter

I noted that messages arrived (as the filter is applied) in the offending Folder, with a non-Junk status but after about a second, all arriving are updated as Junk??? Mysterious !

What I might do if no one else has any suggestions: a) Create a new Folder b) Change the Filter to direct all matching emails to the New Folder c) Transfer all messages from the Old Folder to the New

Cheers Sanjay... I noted that messages arrived (as the filter is applied) in the offending Folder, with a non-Junk status but after about a second, all arriving are updated as Junk??? Mysterious !

R. click that folder > Properties. What is filled in at the Location field?

Hi... nothing untoward in the Location field. Same imap setting as per other Local Folders (that are also populated with Filters), except of course for the Folder Name. R

Hi... nothing untoward in the Location field. Same imap setting as per other Local Folders (that are also populated with Filters), except of course for the Folder Name. R

Proceed! a) Create a new Folder b) Change the Filter to direct all matching emails to the New Folder c) Transfer all messages from the Old Folder to the New

Cheers... Have done so. Will advise if successful, as new messages arrive. R

Cheers... Have done so. Will advise if successful, as new messages arrive. R

Quick pre-arrival test: copy any Inbox message to each of the folders. Theoretically, the one copied to the funky folder should become junk; the one copied to the other, not.

Hi... Had actioned the Create New Folder / Reroute Filter / Move all Messages / Delete Old Folder However, I: 1) Manually moved an Inbox msg to the New Folder. All good. 2) Moved an old msg from the now populated New Folder, to Inbox and let the Filter run again. All good. Fingers crossed... resolved. Thanks