How do I set the sender name? When emails are sent from my dev drupal site to new users the sender is listed as the first part of the site's email address ("info" from "info@mydomainname.com.au" (screenshot below)). Ideally I would like it to be the site's name. How can I control this? Thank you.
drupal_mail() supports a display name in the From: field, but it's up to the whatever module you're using to send mail. If you'd like to force the name, you can use the MIMEMail module.

Once installed, under the Configuration > System > Mimemail administration menu, you can set the default Name/Email that will be sent.