Thanks for the new comments. Just noticed them since I wasn't checking for a few days since no one had commented since the initial reply.
I've continued to use the filter moving the spam that had "noreverse" into it's own folder. It's been almost a month and so far the spam (score>=5) + norevese test hasn't had any failures.
It was mentioned that "it would be a mistake to assume that a message should be discarded simply because a reverse entry can't be found". But remember I am also checking the spam score as well. Does that change the argument any?
I appreciate the comments on the reliability (or lack of it) of using noreverse as a filtering criteria. This is the kind of info I was asking for in my decision to even keep this additional stuff. I might just end up taking it out and let it end up in the normal spam folder.
FWIW I would estimate more than 90% of the spam I've been getting also had noreverse and thus ended up filtering into my "noreverse" folder which is how I came up with that 90% number (didn't actually count them though). Given that statistic maybe it isn't worth the added test if I cannot trust the reliability and just let the stuff end up in the spam folder where it was originally destined. But hey, at least I got to play with sieve a little.
