Email FROM: server_default_name rather than %name <%email>

My webform test emails are set up to use the name and email fields for FROM: .... but that's not happening. They messages are coming FROM: username@sharedhostingaccount.com

The subject line and conditional recipient are working -- only the FROM is not.

I have a homegrown PHP script on another (non-Drupal) site on the same server account that manages to populate the FROM field using data input from a form, so I know it's possible. How can I get this to work here?