It sounds like you’re referring to this thread. I recommend that you follow my first suggestion there, which was to record a sample log of what Mail is doing to figure out why it’s slow. Otherwise you will be guessing at a solution that may be for a different problem than the one you actually have. Please start a new e-mail or thread for your issue.
SpamSieve needs to detect whether Mail has finished launching in order to know whether it should temporarily disable its rules. To do this, it asks Mail to count the number of mailboxes. In rare cases, Mail is very slow at doing this, and so what should be a simple query ends up causing Mail to hang. This seemed to be what was happening in the other thread, so I asked that customer to click this link to set an esoteric preference not to ask Mail to count the mailboxes. In your case, that wasn’t the source of the problem, and so avoiding the counting caused SpamSieve to believe that Mail had finished launching when it actually had not, hence the rule problems that you saw. So you should click this link to turn the counting back on.