SMTP stands for Simple Mail Transfer Protocol. It is a widely used communication protocol for sending and relaying email messages between servers. SMTP is an essential part of the email infrastructure and is responsible for the transfer of outgoing mail from a sender’s email client or server to the recipient’s email server.
Here’s how SMTP works:
- Sender initiates the connection: When you send an email from your email client or application, it connects to your email server using SMTP to transmit the message.
- Sender provides recipient information: The sender’s email client or server provides the recipient’s email address, sender’s address, message content, and other necessary information to the SMTP server.
- SMTP server relays the message: The sender’s SMTP server establishes a connection with the recipient’s SMTP server. It communicates with the recipient’s server and transfers the email message. If the recipient’s server is not directly reachable, the sender’s server may relay the message through intermediate SMTP servers until it reaches its destination.
- Recipient’s server delivers the message: The recipient’s SMTP server receives the email, processes it, and stores it in the recipient’s mailbox for later retrieval.
SMTP operates over the TCP/IP protocol suite and typically uses port 25 for unencrypted communication and port 587 for encrypted communication (STARTTLS or SSL/TLS) to ensure the security and confidentiality of email transmissions.
SMTP is responsible for routing and delivering email messages, but it doesn’t handle the retrieval of emails from a mailbox (this is typically done using protocols like IMAP or POP3). It plays a crucial role in the email ecosystem, enabling the reliable transfer of email messages across the internet and within email networks.