In an STP-enabled switch, the port statuses that may exist include Forwarding, Listening, and Disabled. The Forwarding state allows data frames to be sent and received on the port. The Listening state is where the port prepares to forward data frames but does not yet send or receive them. The Disabled state means the port is not participating in the STP process and does not forward frames. Although the 'Discarding' state exists in RSTP (Rapid Spanning Tree Protocol), it is not traditionally listed under the standard STP port states.