Seconding this. I’ve struggled for years to get message forwarding working correctly and briefly toyed with setting up PostSRSd with essentially no success. The only thing I’ve been able to do to get forwarding to work is by making use of Postfix’s generic map, which, while functional, is certainly not easy for the average user to set up or keep functional.
Either the external alias forwarding should be updated to work correctly with SRS, or the functionality should be removed entirely.