Regarding the sequence of the mail transmission process, which of the following is correct?

1. The sender PC sends the mail to the designated SMTP Server.

2. The sender SMTP Server encapsulates the mail information in an SMTP message and sends it to the receiver SMTP Server according to the destination address of the mail

3. The sender SMTP Server encapsulates the mail information in an SMTP message according to the destination address of the mail and sends it to the receiver POP3/MAP Senver

4. The recipient sends an email.