Customize the canceled meeting email

Hi joao_ramos,

I suppose that this is a message coming form the resource mailbox (a.k.a meeting room).

You can customize the auto-response message you get from Exchange when booking a meeting room.

Here are the steps to do it using the Exchange Admin Center:

1.In the Exchange Admin Center, click the “Resources” tab under Recipients.
2. Click on the name of the resource mailbox you would like to edit.
3. A side panel with information about the meeting room will appear.
4. In here, click on 'Booking’, then on "Manage booking settings".
5. Under the section “If you want the meeting organizer to receive a reply, enter the text below.”, you can enter the custom message.
6. Click save.

Manage resource mailboxes in Exchange Online | Microsoft Learn