Carriers are required only when you are using an SMTP gateway.
Carrier properties set up public wireless carrier configuration, which provides carrier-specific information such as how to map automatically-tracked phone numbers and network providers to SMS email addresses.
Carrier information is used when the device tracker gateway needs an SMS email address to be generated from an automatically-tracked device address. Addresses are generated in the following form:
email-address = sms_email_user_prefixphone-number@sms_email_domain
sms_email_user_prefix is the value of the sms_email_user_prefix property
the phone number comes from the ml_device_address.address column
sms_email_domain is the value of the sms_email_domain property
For more information about carriers, see Gateways and carriers.
For more information about setting properties, see Setting properties.