The mail server requires authentication before accepting mail. You must log in to send.
SMTP error 530 means the server requires you to authenticate:
Your mail client or server isn't sending authentication credentials.
SMTP authentication is not enabled in your email client settings.
The server requires a secure connection (STARTTLS) before accepting authentication.
In your email client settings, enable 'My outgoing server requires authentication' or similar option.
Provide your username (usually email address) and password for the SMTP server.
Enable TLS/SSL for the SMTP connection. Try port 587 with STARTTLS or 465 with SSL.
If using 2FA, generate an app-specific password for your email client.
530 5.7.0 Authentication required
530 5.7.1 Client was not authenticated
530 Must issue a STARTTLS command first