Gerry,
Okay - I can find some sieve config files (90-sieve.conf) but a full port scan of the local host does not show Sieve listening on any port.
By contrast I kept an image of my 'old' abandoned Lion server disk which has sieve listening on 4190.
My ML server was a new Mac mini to replace my failed SL Sever (multiple disk failure). It was restored from a time machine backup of the SL Server to restore all the users, websites and mail stores. I don't know if this has impacted Sieve but I cannot get any response or find any information on how to proceed with this.
I would love a solution as my my late 2012 Mac mini server won't boot ML Server (i have tried all of the instructions on here) in any form so I have fallen back on a very old early core duo machine to run the time machine restore of my super reliable SL server.
Nick