'Folders in your mailbox have name conflicts'

I have an outlook email address (@live.co.uk) - I use the Mail app on my Mac, iPad and iPhone.

I receive the same email several times a day stating:

One or more folders in your mailbox have name conflicts with others or system reserved names.

Folders with these names can't be downloaded by your IMAP e-mail program.

Junk

Please connect to your mailbox using your Web browser and rename those folders. Once renamed, those folders will be displayed in your IMAP e-mail application correctly.

How do I stop this from happening?