@JdeRocquigny sending to a group (mass email, etc.) is definded as a marketing email in HubSpot. Here are a couple of resources:
So your team would need to make the email as a marketing email, then create the list(s) you want to send it to, and send it. You can send emails from contact owner, so it will come from the specific sales person, and by using personalization tokens it will use the contact’s first name.
That’s how you’d send to a group. And each contact record will show the emails in them, too.