Rich Bishop: > Sep 30 20:22:18 jay postfix/qmgr[10510]: qmgr_transport_throttle: transport > smtp: status: 4.3.0 reason: unknown mail transport error > Sep 30 20:22:18 jay postfix/qmgr[10510]: warning: transport smtp failure -- > see a previous warning/fatal/panic logfile record for the problem description
As the logfile says, search the logfile for warning/fatal/panic records. See http://www.postfix.org/DEBUG_README.html#logging for instructions. Wietse