A customer has the domain customer.com and registers ICON-systems with their own e-mail based video numbers.
For example, one video system would be registered as firstname.lastname@example.org.
DNS etc are properly configured and external parties can reach the customer using email@example.com.
However when the ICON-system dials out the receiving system will see it's displayname followed by firstname.lastname@example.org, not the custom video number the customer has chosen.
Make this configurable!