Fix a PHPMailer/Apache error and configure the Adult Video Script SMTP

I'm configuring the Adult Video Script, everything is already installed and technically almost everything is functional, but in the registration part, it always returns an error on log (this one attached) and it also doesn't send any email to the user. So I would like the error to be resolved and the Adult Video Script SMTP to be configured, thanks in advance.

Some relevant information: DigitalOcean Droplet, with Plesk