WHen trying to add IMAP external service, I can't see the IMAP entry in the service TYPE combolist.
Is there any config to do to enable that or any specific licence to add ?
definitely make sure you have the licensing, but also make sure that you have turned on imap in the class of service for the users you want to have it. I chased that problem and not even TAC could find it. They thought it was a licensing issue. I happened to fix it myself by going through every menu and line item and finding it.
Class Of Service
(your users' COS)
Allow Users to Access Voice Mail Using an IMAP Client