You'll probably need to check the settings that the iPad has auto setup for your mail account. It's not unusual for server names to be wrong. Manual setup may be needed.
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The setup is pretty much the same for iPhone and iPad.
If you've got unique emails saved on the iPad's email account that you wish to keep you'll need to save those to a local folder first.
Then delete the POP3 account and add the account back as an IMAP account.
I think you have the problem and I think I need to change from POP3 to IMAP but can't get to an appropriate screen through my IPAD settings. Can you advise
[Check that iOS is up to date!]
@MrWit, in the 'Add Account' screen, do not use the 'Outlook.com' option, use the 'Other' option, and then 'Add Mail Account'.
If you continue to run into problems, repost ..............