[X4U] Why is Mail filtering into the Trash folder?

[Crandon David]

Hello Everyone,

I use OS 10.4.11 with Mail 2.1.3 (753.1/753).

About once every 50 messages or so, for the last year or so, Mail  
will filter a message into the Trash.

I have no filters set to filter anything into the trash.

Sometimes it's a private message, sometimes it's a message from an  
listserve I belong to. It never seems to be a spam message, those  
either get to my spam folder or come through like a regular message.

Can anyone offer some insight?

Thanks,

David