E.123 is an international standard by the standardization union (ITU-T). It provides guidelines for the presentation of telephone numbers, email addresses, and web addresses in print, on letterheads, and similar purposes.
As described by the ITU, in E.123: "+" is the "International Prefix Symbol" used in a "Telephone number, E.123 international notation". For example:
Telephone number, national notation (full number dialling)
(0607) 123 4567
Telephone number, E.123 international notation
+22 607 123 4567
An ITU-T (International Telecommunication Union - Telecommunication Standardization Sector) standard that defines global telephone number format. As described by the ITU, the E.164 general format must contain only digits split as follows:
A leader plus sign (`+`)
Country code (max 3 digits)
Subscriber number (max 12 digits)
For example, a US phone number would be rendered like this: [+]
The following examples demonstrate the format:
US phone number: +11234567890
UK phone number: +4407123456789
SE phone number: +461234567890
We often refer to a telephone number as a MSISDN – Mobile Station International Subscriber Directory Number – for example, a telephone number using international E.164 format. This term is used in quite a few messaging documents. It is sometimes pronounced as “miz-din.” The term: MDN – or Mobile Directory Number – also refers to a telephone number, using the international E.164 format.
Enhanced Messaging Service - An EMS-enabled mobile phone can send and receive messages that have special text formatting (such as bold or italic), animations, pictures, icons, sound effects and special ring tones. EMS messages that are sent to devices that do not support it will be displayed as SMS transmissions. EMS is a cross-industry collaboration between Ericsson, Motorola, Siemens and Alcatel, among others.
External Short Message Entity. The ESME receives a message from a customer. A connection is established with an SMSC, and then that message forwarded on to the SMSC for delivery to a destination recipient. You are an ESME.
European Telecommunication Standards Institute - ETSI is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standards for ICT-enabled systems, applications and services.