When you click Send Email to send an email to a singer, it prepares an email addressed to that singer IN THE EMAIL SYSTEM THAT YOU HAVE SET as your default email system on this computer.  If this is not the email system you use, you can

1. go to the settings on this computer and change your default email system to the system of your choice.  Then click Send Email again.

or

2. Copy the email address for this singer from the prepared email and paste it into an email in your email system of choice.