Does reading a message change SpamSieve's prediction?

I’ve set up SpamSieve in the drone configuration with Apple Mail. Because the drone is set up to check email every 5 minutes, I sometimes see spam messages appear in my non-drone inbox (if I check mail after a spam has been received but before the drone has seen it).

Now here’s the funny thing… Accidentally clicking one of those spam-to-be messages, which causes Mail to mark it as read, seems to affect SpamSieve’s prediction. That is, it seems as though SpamSieve will not mark spam I had clicked on as spam (or at least is much less likely to). Is there any possibility of this, or am I imagining things?

Marking the message as read will cause Mail (on the drone) to not think it’s a new message, so Mail will not apply the rules (and, thus, SpamSieve) to it. So it’s not changing SpamSieve’s prediction, but rather preventing it from making a prediction.

Hmm, so I guess the root of the problem is that my drone isn’t retrieving email frequently enough for me not to see it.

On a somewhat related topic… If only I could get IMAP IDLE working on the drone, then problem solved. My email provider (DreamHost) claims to support IDLE, but it’s never worked for me with Apple Mail.

Are there any SpamSieve users here who have gotten IDLE work on Mail…or any other client?