I've been using Opera's M2 mail client for over a year now, and I really am hooked on their filter system.  Essentially all messages are in one database, and the filters are like database views.  This way you only ever have one copy of the message.  Gmail is using the same idea with their labels.

Are TBs filters like this?  While I really like the filters in Opera, it doesn't have S/MIME support.  I see from the product description that TB does support S/MIME.  If TBs filters are like Opera's or Gmail's, I'd most likely switch.

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andrewdied