Hi Sonny,
The problem that you are facing it usually happens when you exceed the maximum storage space for contacts, Hotmail provides to add up to 500 contacts, and in very rare scenarios you might be able to add more than 500 contacts, but you might face problems later, like deleting, updating, unable to add contacts and also duplication of contacts.
In order to resolve the problem please go through your contacts and delete unwanted contacts and duplicate contacts, and try to reduce the number of contacts in your address book to 500, this should help you to resolve the problem.
How to remove duplicate contacts?
- Go to your contacts (people) page on Hotmail.
- Click on manage and select clean up contacts.
- Select remove duplicate contacts.
Thanks and regards
Mubarak Pasha