About NAPTR Records

ENUM uses NAPTR records for URI resource records. NAPTR records are used to translate E.164 addresses to SIP addresses. An example of a NAPTR record is:

$ORIGIN 4.3.2.1.5.5.5.2.0.2.1.e164.arpa.
IN NAPTR 100 10 "u" "sip+E2U"  "!^.*$!sip:[e-mail]!"

This example specifies that if you want to use the "sip+E2U" service, you should use sip:[e-mail] as the address.

The regular expression can be used by a telephone company to easily assign addresses to all of its clients. For example, if your number is [phone], your SIP address is sip:[e-mail]; if your number is [phone], your SIP address is sip:[e-mail].