I cannot send emails

That is unfortunate, but unless you can offer more information like the actual error message you get when trying to send mail and the details of the mail provider you are using no one will be able to do more than commiserate.

Sending of the message failed. An error occurred while sending mail. The mail server responded: This email was not sent but there is a way to fix it. To resend successfully you need to update your email settings (e.g. Outlook) to turn SMTP authentication on. For guidance on how to do this please visit: https://www.telstra.com.au/support/email/unauthenticated-traffic-limit Reference: OB315 e{234e697d-7174-4a2d-95c8-51b2a3b1a2cf}. Please verify that your email address is correct in your account settings and try again.

This is the message I get when I try to send and email