Access an Office 365 shared mailbox on iOS 9 & 10

Choose Settings

Mail, Contacts, Calendars

Choose Add Account.

Choose Other

Add Mail Account.

On the New Account screen, enter the following:
Name: the name of the account
Email: [email protected]
Password: your password
Description: description of the account

Choose Next.
Make sure that IMAP is selected at the top of the screen.
Incoming Mail Server:
Hostname: outlook.office365.com
User Name: [email protected]/support (the alias of the shared mailbox)
Password: your password (This may have been auto-filled)

Scroll down to the Outgoing Mail Server section and enter the following:
Host Name: smtp.office365.com
User Name: [email protected]
Password: your password

Choose Next and wait for the server to verify your settings. When complete choose Save.

The shared mailbox should now appear within the mail app