The purpose of the concept is to use the mechanisms of the internet domain name system (DNS), a hierarchical, distributed system, to store information directly related to telephone numbers and to make this information available to a community of users or operators. 

Originally designed to enable users with an E.164 telephone number to publish, after the corresponding domain name, additional information on their means of communication (e.g. mobile telephone number, fax number, voice messaging number or address, e-mail address, etc.), ENUM is increasingly perceived as a key element in the Next Generation Networks (NGN). In fact ENUM is also being used by operators as a universal database which makes it possible to store various forms of information relating to each E.164 number. One practical example is the storage of the information required to route calls to E.164 numbers. This implementation of ENUM has been named "Infrastructure ENUM" - or ENUM carrier or operator - in contrast to "User ENUM", which is the basic idea aimed at users, but which has not been as successful as expected.

• informing participants about User ENUM, the current work in progress towards international standardisation and the initiatives launched in various European countries;

• discussing the possible formation of a working group to launch a coordinated User ENUM project in Switzerland.

On 22 January 2003 a kick-off meeting was organised by SICTA and a working group was set up.

After three meetings of the working group, it became apparent that only one company (SWITCH - www.switch.ch) was interested in actively participating in evaluation of User ENUM functionalities by setting up a pilot infrastructure. The working group then decided unanimously to put a hold on its activities, giving SWITCH the possibility of taking the necessary steps with OFCOM in order to obtain temporary authorisation to operate the zone ''1.4.e164.arpa''.

In September 2003, OFCOM granted Switch, at the latter's request, a provisional licence with a 2-year term for the management of User ENUM domain names in the "1.4.e164.arpa" zone within the framework of a project to assess the functionalities associated with User ENUM. This licence was extended for a further two years in September 2005, expiring on 30 September 2007.

During the month of May 2007, OFCOM consulted the companies which had taken part in the User ENUM evaluation phase as well as any interested person or organisation with a view to determining the appropriate follow-up to the User ENUM project in Switzerland. From more than 450 invitations sent out, only 6 comments were sent to OFCOM. The consultation report, available in PDF format from the link below, concludes from this that User ENUM is no longer necessarily a highly topical subject and draws up a list of 4 points to be considered in any transition to productive and commercial use of the registration of User ENUM domain names.

• Evaluation report on the consultation of interested parties concerning the follow-up to the User ENUM project in Switzerland (June 2007)
  (available in german or french only)

Between July and September 2007, contacts took place between OFCOM and Switch, the main party interested in pursuing the User ENUM project in Switzerland. On the basis of the consultation report produced several months previously, OFCOM specified the conditions for the award of a licence for the productive and commercial use of registration of User ENUM domain names. After a period of reflection, Switch decided to abandon the project.