You can edit the WorldClient templates so that users can mark mail as spam for the bayesian learning program to train from. (Note that MDaemon 9.5+ has built-in support for this in the Lookout and Simple themes.)
The idea is to have two separate delete buttons, one for normal 'delete' and the other for 'delete-as-spam'. The delete-as-spam button will move the mail from the user's mailbox into the SpamFilter training folder for False Negative.
This
example is for the Globe theme but can be altered to be used with other
themes. Also, this example uses the same delete button that is already
present. If desired you can create your own delete-as-spam button and
use that for clarity.
Changes to make:
Additional Comments
This type of configuration should be used with caution as the
bayesian program cannot account for user error. If someone marks a
message as spam, this will train the bayes program for all users in
MDaemon to think of that message as spam.
Template customization is only available in MDaemon Pro.