Please see lines 357-374 in talkback.php for reference to "Anonymous." That is the default.
In regards to the PHPMailer issue, the settings are dependent on how your IT department has your SMTP servers configured. For example, our IT department doesn't require a username password, but it does require SubjectsPlus to be whitelisted on their smtp server. The reason ours is not working is because we are in the process of migrating our instance of SubjectsPlus to a new Azure App Service Plan and it has not been white listed yet.
Please use the PHPMailer documentation to determine what settings are required for the SMTP server at your institution.