'Salutatory Email for Clients' wrong CP and manual URL

[greenpete]

I have a problem with the 'Salutatory Email for Clients'.
When I create a new user the system sends an e-mail with all the details in, but the CP URL and the Manual URL have the local IP in them instead of my domain name.
i.e. I get;
Your Control Panel can be found here https://192.168.0.6:81
instead of;
Your Control Panel can be found here https://www.mydomain.com:81
Can anyone tell me how to rectify this please.