If for some reason the client does not want to use the mail application like web mail or Horde. If the user does not want to disable this kind of setting for any account within the hosting interface; it can also be done by inserting a small file. The user can either be an administrator of the server or he can be reseller with shell access. It just takes a few steps to  do so.

Suppose you want to disable ‘Horde’ for user_jeffrey account then you just need to get into shell and fire following command vi /var/cpanel/users/user_jeffrey
The user has to add the following lines :-

skiphorde = 1
skipneomail = 1

Similarly, if later a client or user would like to enable the setting. This can be done with some small changes and by editing the internal code to ‘0’ in above described code.
Note- As soon as you amend the above mentioned changes with in that file you have to make sure that you restart the service.