Email account expiration is explained at https://confluence.esg.wsu.edu/pages/viewpage.action?pageId=142509221 

Office 365 software is only available to students and employees while  they are actively enrolled or employed at WSU. When this association ends, these subscriptions are cancelled in about a week. If your connection to WSU is ending and you want to buy a new subscription, you may do so at https://products.office.com/en-us/buy/office. If you do not do so, you will want to download to your local computer any documents that you may have in OneDrive, if you have used that service.