Rogue imap folders

I have a MacBook Air with OSX 10.9 which I have set up to work with my

my office email through imap. There are folders called "Chats",

"Contacts" and "Emailed Contacts", which I did not create, that are

visible using Mail but not with another imap client and not with our

web based mail interface. I cannot delete them or rename them, the

imap server returns an error. I have tried deleting the imap account

from mail and then adding it back again and this did not help. I

presume that these folders are an Apple specific functionality that

has been corrupted somehow.

The history may be important. Initially I set it up the account as an

Exchange account, hoping to get both email and calendar working at the

same time but for whatever reason this is not possible. So I set up

the calendar and imap separately, but perhaps that initial step is

when the folders were created. Later I moved my imap mail prefix to

the higher folder possible and this is when the folders becam aparent.

These folders are rather annoying and it concerns me that they may be

a sympton of a deeper problem. Can anyone shed any light?