$echo"Authorization: Basic$(echo'<client_id>:<client_secret>'|base64)"#Result:#Authorization: Basic U1ZOT1JGQlVXR2h4V0daU1VVbDBlQT09Ojc1Yzc0NDQ3LWM0YWYtNDUzYi1hZDA2LTNhOGFlOTY5ZWQxNg== 3. Send E-Mails Plain text or HTML $ curl -XPOST \ -u'<client_id>:<client_secret>'\ -H'...