vice. It is quite common in current telecom management applications to have alerts and summary reports sent by mail from the EMS, NMS, and OSS/BSS solutions to the concerned operator or business manager. SMTP (simple mail transfer protocol) has been used as the mail service protocol to explain the concepts of communication by mail. 29.1 Introduction The standard mechanism for electronic mailing on the Internet for sending a single message that includes text, video, voice, or graphics to one or more recipients is known as simple mail transfer protocol or SMTP. The electronic message called mail has an envelope containing the sender address, the receiver address, along with other information. The message has a header part and a body. The header has information on destination and source, while the body of the message holds the content to be read by the recipient. The header has: The sender address: Details of the address from which the message is sent. The receiver address: Details of the recipient address to which the message is to be sent. Message subject: An identifier for the message. The Internet user having an e-mail ID receives the mail to his mailbox that is periodically checked by the e-mail system and informs the user with a notice. If the Fundamentals of EMS, NMS and OSS/BSS user is ready to read his mail, a list containing the information about the mail like the sender mail address, the subject, the time when the mail was sent or received are displayed. The user can select the message of his choice and the contents of the message is displayed on the screen. E-mail addresses are required for delivering mail. The addressing system used by SMTP consists of the local part and the domain name that are separated by an @ symbol (local_identification@domain_name) Some of the terminologies that the reader will encounter in this chapter are: User agent: The user mailbox stores the received mails for a user for retrieval by the user agent. Email address: The name of the user mailbox is defined in the local part of 