Very strange... I did, what everybody does, when something is not longer working as expected (remove / reinstall) and Avast uses again ports 12xxx.
Now it would be interesting, what caused Avast to abort using 12xxx and start using 39xx. It seems as Avast just used new ports for the whole mail-sacnning-subsystem (12080 stayed!).
Maybe one of the Avast developers could bring some light into this issue...