Custom email login details based on specific usergroup

I have a context web and intranet. Intranet is available for users in usergroup intranet. The usergroup only has access to context named intranet. Now I want to change the body of the email send to new created users in usergroup intranet without the manager link in email body.

My suggestion was to create custom settings on the usergroup and adding custom text for setting signupemail_message so when a user is created in specific usergroup this email would be sent, but no luck. It still sends standard email with link to manager and suggest user can login in backend en change the content. Users in usergroup intranet only have access to frontend by login.

What am I missing?

Anyone?