send mail through your Brevo account
When on, each recipient above is added as a BCC instead of To, so no one sees the other addresses. The To field will show your own sender address.
This page calls the Brevo API (api.brevo.com/v3/smtp/email) directly from your browser using the key above. If the request is blocked by your browser with a CORS error, Brevo's API isn't allowing direct browser calls from this origin — in that case you'll need a small server-side relay instead of calling it client-side. Your API key is never transmitted anywhere but Brevo.
api.brevo.com/v3/smtp/email