Describe the addressing system used by SMTP.
The correct answer and explanation is :
Correct Answer:
SMTP (Simple Mail Transfer Protocol) uses email addresses that follow the format user@domain as its addressing system.
Explanation (300+ words):
SMTP (Simple Mail Transfer Protocol) is the standard protocol used to send emails over the Internet. It is part of the application layer of the TCP/IP protocol suite and is responsible for the delivery of email messages from the sender’s mail server to the recipient’s mail server. The addressing system used by SMTP is based on email addresses, which uniquely identify the sender and recipient of an email.
An SMTP email address follows the format:user@domain, where:
userrepresents the username or the local part, which identifies a specific mailbox or user account on the mail server.domainrepresents the domain name of the mail server that hosts the recipient’s email account.
For example, in the email address john.doe@example.com, john.doe is the user, and example.com is the domain.
SMTP relies on the Domain Name System (DNS) to resolve the domain part of the email address into an IP address of the recipient’s mail server. It uses a specific type of DNS record called an MX (Mail Exchange) record, which tells the SMTP server which mail server is responsible for receiving emails for that domain.
Here’s a basic outline of how SMTP handles addressing:
- The sender’s mail client uses the recipient’s email address (e.g.,
alice@xyz.com) and connects to the sender’s SMTP server. - The SMTP server extracts the domain (
xyz.com) and queries DNS for the MX record. - Once the IP address of the recipient’s mail server is found, the sender’s SMTP server establishes a connection to it and transmits the message.
SMTP does not understand or care about display names (e.g., “Alice Smith alice@xyz.com“)—it only uses the user@domain format for actual delivery. This standardized addressing ensures that messages are correctly routed across the global internet infrastructure.