Because you have migrated the post office to Linux, the source POA no longer has an active post office to service and the MTA can no longer communicate with it. Therefore, the source POA is no longer a necessary part of your GroupWise system.
Go to the source NetWare or Windows server where the original POA is still running.
Display the POA server console.
Stop the original POA on the source server.
Continue with Performing the Second Stage of Post Office Data Migration.