Hey Stephan
You can use sendgrid to send to multiple recipients
You will need to install @sendgrid/mail
tutorial link i have created and working
https://support.totallycodable.com/en/article/send-a-template-email-using-sendgrid-npm-and-wix-code
document link to send multiple recipients
to: ['recipient1@example.org', 'recipient2@example.org'],