This tutorial will show you how to set up your Office365 mail account on an iPhone or iPad using Apple Mail.
Note that there are known issues with Office 365 and Apple's native Mail app so you may prefer to use the Outlook iPhone app as this has the same look and feel as the web and desktop Outlook. See here: https://support.rezolve.co.uk/index.php?/Knowledgebase/Article/View/713/0/using-outlook-for-office-365-on-iphone-or-ipad
1. Open your Settings and go to 'Mail, Contacts, Calendars'
2. Tap 'Add Account'
3. Tap 'Exchange'
4. Enter you email and password and give the account a decsription. Tap 'Next'.
6. You should be automatically directed to step 7. If you are taken to a screen like this instead, you will need to re-enter your username and password (your username is your email) and you will need to enter 'outlook.office365.com into the Server field. Then tap Next.
7. Choose the iPhone items you wish to sync with your mail account and hit 'Save'.
Your Office365 mail is now set up on your iPhone/iPad :)