Configure the External Postmaster Address
If, like me, you have configured multiple domains on your Exchange server, you may want to change the default postmaster address. This is used as the sender for system generated messages and notifications. It’s quite simple to change this and here is how:
1. In the Management Console tree navigate to Organization Configuration -> Hub Transport then select the Global Settings tab
2. Right-click Transport Settings and choose Properties
3. On the General tab enter the desired postmaster address and click OK
If you prefer to use the PowerShell to do this then here is the command:
Set-TransportConfig -ExternalPostmasterAddress firstname.lastname@example.org
Note: this change isn’t replicated to any Edge Transport Servers in the organisation – you’ll need to configure them manually.