The migration to Exchange Online, Microsoft’s hosted cloud service, is taking longer than testing indicated it would. Presently 1200 of 5300 users (22%) have been switched over since the 3:00 AM start time. The rest of the users should be moved over the course of the day.
There may be delegate issues during the transition as they are not supported between cloud users and “on premise” users.
More information is available at https://www.csuchico.edu/email.