You can add an Exchange Shared mail box to an iPhone or iPad as follows. 

Note:  If you are using the Outlook App on your device scroll down to Outlook iOS App section below.

Native Mail App instructions

1. Go to Settings > Passwords & Accounts.
2. Click Add Account.
3. Select Other.
4. On the Other screen, touch Add Mail Account.
5. In the new screen, you will enter: 
   • Name: The name that will be displayed to recipients on email.
   • Email: The email address of the shared mailbox (e.g., user@domain.com).
   • Password: Your Office 365 email password.
   • Description: Your chosen description.
6. Touch Next to get to the full settings.
7. On the following screen, confirm that IMAP is selected at the top.
8. Scroll down. In the Incoming Mail Server section, enter the following values:
   • Host Name: outlook.office365.com
   • User Name: Your personal email address, followed by a forward slash, followed by the name of the shared mailbox. For example, user@domain.com/shared
   • Password: Your Office 365 email password.
9. Scroll down. In the Outgoing Mail Server section, enter the following values:
   • Host Name: smtp.office365.com
   • User Name: Your full Davidson email address.
   • Password: Your Davidson email password.
10. Touch the Next button and wait for the server to verify your settings.
11. Choose your synchronization choices and touch Save in the upper right corner. You will now find the shared account in your Mail app under Mailboxes.

Outlook iOS App instructions

1. In the Outlook App, tap on the 3 vertical lines in the top right corner, then select the "Settings" icon (looks like a cog-wheel) a the bottom.
2. On the Settings screen, choose "Add Account", then choose "Add Email Account". Enter the name of the shared account (example: sharedaccount@domain.com), then choose Add Account. This will take you to an office 365 login screen asking for a password. Since it is a shared mailbox and you most likely do not have a password, click the back arrow in the top corner. There is a new option on the screen called "Setup Account Manually" choose that option.
3. On the next screen, scroll down to where it says ADVANCED and select IMAP.
4. Turn on the switch for and Use Advanced Settings and enter the following information:
   • Email Address:  (enter_the_name_of_the_shared_mailbox)@domain.com
   • Display Name: What you want the mailbox to be called
   • Description: You can leave blank
   • IMAP Hostname: outlook.office365.com
   • IMAP Username:  (your_primary_account)@domain.com\enter_the_name_of_the_shared_mailbox
   • IMAP Password: YOUR account password
   • SMTP Hostname:  smtp.office365.com:587
   • SMTP Username: (your_primary_account)@domain.com
   • Password: YOUR account password
5. Select Sign In. If all the information you entered is correct, you will now have access to the shared mailbox on your iOS device.

Note:  If you have entered domain.com anywhere that is an example replace it with your own domain!