Sometimes you need to send a message as a group rather than as yourself. In these situations, the group's mailbox has to be configured to allow specific people to be senders. To have this configuration completed, please open a ticket.
Once the configuration is completed, follow the steps below to send a message as a group from your personal mailbox.
1) Log in to Office 365/Outlook on the Web
2) Click "New Message"
3) Click on the "From" button next to your address in the new mail message and click on "other email address" (if you don't see the "From" button, follow these steps)
4) Type in the name of the group you're sending as until the name of your group comes up. Click on your group name. In this example, firstname.lastname@example.org
5) Compose and send the message as normal, and the recipient will see it as coming from that group rather than your personal account. For future messages, your group name will be saved, so all you'll need to do is click the "From" button and select your group.
***Note: If the group hasn't been configured to allow you as a sender, your message won't go through.