Step-by-step

   

  1. Go to Settings > Mail > Add account  (in iOS 11-13 go to Settings > Accounts & Passwords > Add account) (iOS 14 -  Settings > Mail > Accounts > Add Account)
  2. Select Other from the list of types. 
  3. Tap Add Mail Account.
  4. Enter a name for the mail account (e.g. IT Shared Mailbox)
  5. Enter the email address of the shared mailbox
  6. Enter the password of a mailbox that has access to the shared mailbox (e.g. your own password)
  7. Enter a description for the mailbox (e.g. Shared Departmental Mailbox)
  8. Tap Next.
  9. Select IMAP
  10. Fill in the following:
    Under Incoming Mail Server
    Host Name: outlook.office365.com
    User Name: [email protected]\[email protected]
    Password: Your email’s password

    Under Outgoing Mail Server
    Host Name: smtp.office365.com
    User name: [email protected]
    Password: Your email’s password
  11. Tap Next, then tap Save.
  12. In the next screen, choose which items to sync (generally just emails)
  13. Tap Save.
  14. Exit Settings and start the Mail app.