Set up a shared mailbox on your iOS device (iPhone, iPad)

Instructions

Go to Settings > Mail > Add account (in iOS 11 go to Settings > Accounts & Passwords > Add account).
Select Other from the list of types.
Tap Add Mail Account.
Enter a name for the mail account (e.g. Shared Mailbox).
Enter the email address of the shared mailbox.
Enter the password of a mailbox that has access to the shared mailbox (e.g. your own password).
Enter a description for the mailbox (e.g. Shared Departmental Mailbox).
Tap Next.
Select IMAP.
Fill in the following:
- Under Incoming Mail Server:
  - Host Name: outlook.office365.com (this should work as is, but if you wish to insert the port number, it can be added to the end of the host name, preceded by a colon – e.g. outlook.office365.com:993)
  - User Name: Enter the email address of the account that has access to the shared mailbox, followed by a “\” and then the email address of the shared mailbox itself (e.g. firstname.lastname@utoronto.ca\shared.mailbox@utoronto.ca). Please note if a single backslash does not work, try inserting two (e.g. firstname.lastname@utoronto.ca\\shared.mailbox@utoronto.ca)
  - Password: Enter the password of the mailbox with the permission to access the shared mailbox
- Under Outgoing Mail Server:
  - Host Name: smtp.office365.com (this should work as is, but if you wish to insert the port number, it can be added to the end of the host name, preceded by a colon – e.g. smtp.office365.com:587)
  - User Name: Enter the email address of the mailbox with the permission to the shared mailbox (e.g. your firstname.lastname@utoronto.ca email address)
  - Password: Enter the password of the mailbox with the permission to access the shared mailbox
Tap Next, then tap Save.
In the next screen, choose which items to sync and tap Save.
Exit Settings and start the Mail app.