On the evening of Tuesday, September 15 IITS received notifications from instructors that Cougar Courses messages were not being received. On Wednesday, September 16 IITS technicians began investigating what was causing the issue. The investigation found that there were two scenarios causing the issue. The first is a change in the Moodle upgrade that impacted the prioritization of forum posts. IITS has implemented an adjustment to the schedule processing to make forum post emails a higher priority. The second is the sheer number of email messages being sent based on changes made to the default forum settings. Some courses had the setting changed to "forced subscription" or "optional subscription" for regular conversational forums (not the News Announcement Forum). These changes generated over 27,000 messages in 24 hours, and as a result, Microsoft saw these messages as spam and blocked the system account a number of times. IITS is advising all instructors to keep the forum subscription configured to the default of "optional subscription".