In some cases you want to allow a user to have several addresses, such as the phone number associated to a main address. You can use Aliases for this purpose.

To add an Alias, use:

#openserctl alias add [email protected] sip:[email protected]
database engine 'MYSQL' loaded
Control engine 'FIFO' loaded
MySql password for user 'openser@localhost':

lookup("aliases"); 

The function lookup("aliases") checks the alias table in the database and if a register is found it translates it to the canonical address (the one in the subscribers table). This feature is also used to redirect DIDs to the final user. There is also the Alias_db module. It searches the alias directly from the database instead of memory. Even, having a small performance penalty, it can simplify the provisioning of alias directly in the database.