Whilst it isn't exactly best practice you may need to set-up a relay on your Exchange 2013 server to allow for email alerts for devices to send alerts to external email addresses.
By default if your devices send emails only to internal addresses you can point them straight at your Exchange 2013 server and without authentication the messages will be delivered to internal recipients. The issue here is if your recipient address is outside of your organization the send will fail.
In order to address this you will need to configure a 'frontend transport' 'receive connector'.
Open 'Exchange Admin Center' and select 'mail flow' from the left menu and 'receive connectors' from the top menu
Ensure you have the right server selected in the 'select server' box and click + to create a new connector
Give the connector a name, in my case I'm calling it 'Local LAN Relay'
Ensure you select 'fronted transport' and set the type to 'Custom (For example, to allow application relay)' and click next
The default adapter bindings are usually OK unless you have a specific need to change this just click 'next'
You will need to edit the IP address range to match your LAN for instance 192.168.0.0/24 will relay mail for the entire 192.168.0.0/24 subnet.
Click 'save' then 'finish' to save the connector.
Now click the 'edit' button to edit the connector you just created.
Select the 'security' option
Uncheck all of the check boxes then on;y tick 'Anonymous users'
Click 'save'
In order to allow the connector to be used with no authentication you must run a simple power shell command.
Open an 'Exchange Management Shell' and issue the following command:
Get-ReceiveConnector “Local LAN Relay” | Add-ADPermission -User “NT AUTHORITY\ANONYMOUS LOGON” -ExtendedRights “Ms-Exch-SMTP-Accept-Any-Recipient”
Replace 'Local LAN Relay' with the name you used for your connector.
You will now be able to relay outgoing email without requiring authentication, great for email alerts from NAS boxes and UPS's etc