Anonymous relays via Exchange 2010

Sometimes you need your Exchange server to allow relaying from scanners, printer units or software that need to push mail directly. If you only need emails to your local users you pretty much dont need to do much, but if you need it to relay to external users, you should make your own receive connector for it allowing anonymous users.

Server Configuration -> Hub Transport -> Create new Receive Connector
Choose an easy name and select Custom for use, set it to use the local IP with port 25 (if you dont want it running on another port or IP), choose which units can relay through it. You can go with either your subnet, or spesific IPs, or a combination if you have several subnets. Finish the wizard and you have your new connector. Now you need to edit it, and make sure only Anonymous users are selected on the Permission groups tab.

When its done, start up Exchange Management Shell and do the following command to give the proper Anonymous rights on the connector.

Get-ReceiveConnector "Name of your new connector" | Add-ADPermission -User "NT AUTHORITY\ANONYMOUS LOGON" -ExtendedRights "ms-Exch-SMTP-Accept-Any-Recipient"

After that restart your Transport service and you should be good to go.