对于发送和接收消息，我们使用两种协议，一种是 SMTP(简单邮件传输协议)，另一种是 POP3(邮局协议版本 3)。它们也分别称为 PUSH 和 POP 协议。它们分别是代理、消息传输代理和消息访问代理，用于发送和检索消息。
SMTP 和 POP3 的区别：
| S.NO | SMTP | POP3 |
|---|---|---|
| 1. | SMTP stands for Simple Mail Transfer Protocol. | POP3 stands for Post Office Protocol version 3. |
| 2. | It is used for sending messages. | It is used for accessing messages. |
| 3. | The port number of SMTP is 25. | The port number of POP3 is 110. |
| 4. | It is a MTA (Message Transfer Agent) for sending the message to the receiver. | It is MAA (Message Access Agent) for accessing the messages from mail box. |
| 5. | It has two MTAs one is client MTA (Message Transfer Agent) and second one is server MTA (Message Transfer Agent). | It has also two MAAs one is client MAA (Message Access Agent) and another is server MAA(Message Access Agent). |
| 6. | SMTP is also known as PUSH protocol. | POP3 is also known as POP protocol. |
| 7. | SMTP transfers the mail from sender’s computer to the mail box present on receiver’s mail server. | POP3 allows to retrieve and organize mails from mailbox on receiver mail server to receiver’s computer. |
| 8. | It is implied between sender mail server and receiver mail server. | It is implied between receiver and receiver mail server. |