If you wish to leave a group (like the BCC film processors), there is a simple way that you can do this yourself instead of emailing the entire group.
If you access Outlook through a web browser:
On the left you should see groups>BCC Film Processors, click on the group name. That will open up the group and you can see any messages etc. Once again click on the group name and that will bring up details of the group. You should see three dots … click on those dots. That will open up a drop down menu with leave group as one of the choices. You could also choose to remain a member of the group and deselect follow in inbox.
If you access outlook through your desktop, it’s a very similar process, but looks slightly different.