macOS Mojave 10.14
Request permission to send emails in Mail on Mac
If you see a message that you need to request permission before your email can be sent, it means the administrator of your Mac set parental controls for your usage of Mail; you can correspond only with approved email addresses.
In the Mail app
on your Mac, click the Ask Permission button in the message.
Mail saves your message in the Drafts folder and sends a request to the administrator who manages parental controls. To find out if your request was approved, check the banner at the top of your message.