We apologize for the inconvenience. We currently don’t support the ability to open shared mailboxes or other mailboxes that you have permissions to access.
To open these mailboxes, you can access Outlook from a desktop browser (by requesting the desktop site in the browser settings) or use the Outlook mobile app that can be downloaded from the iOS and Android app store.
An error occurred while saving the commentmaria.cecilia caballero commented
help me to finish my 365 account. i doubt almost 2 days of signing in and yet nothings done.huhuhu..no outlook.office