Note that you cannot opt out of high-priority announcements. These will be rare, limited to messages that need to get to everyone within a few hours (such as a class cancellation, handling of the system going down, or some other "big" issue).
You are responsible for all clarifications and low-priority announcements made to the discussion forum, whether or not you receive them by email. We expect that you are checking for low-priority announcements at least once every 24 hours during the week. If you don't want the email, log into the forum regularly. Or keep the email coming and set up filters to put the mail in folders that you check from within your mail system. Failure to see a post more than 24 hours old during the week is not an acceptable excuse for not acting on an announcement.