Consider different activities related to email. m1:Send an email from a mail client to mail server m2:Download an email from mailbox server to a mail client m3:Checking email in a web browser Which is the applicable level protocol user in each activity?

For the activities related to email that you’ve mentioned, the applicable level protocols are as follows:

– m1: Sending an email from a mail client to a mail server typically involves the Simple Mail Transfer Protocol (SMTP). SMTP is used for the transmission of emails from the source address to the destination.

– m2: Downloading an email from mailbox server to a mail client can involve the Post Office Protocol version 3 (POP3) or the Internet Message Access Protocol (IMAP). POP3 is used when the mail client connects to the mail server to download emails to the local device, whereas IMAP is used to access and manage emails directly on the mail server, allowing for more versatile handling of emails across multiple devices.

– m3: Checking email in a web browser doesn’t use the traditional email protocols (SMTP, POP3, IMAP) directly from the client side; instead, it involves Hypertext Transfer Protocol (HTTP) or Hypertext Transfer Protocol Secure (HTTPS). These protocols are used for secure communication between the user’s web browser and the web-based email service (webmail server). The behind-the-scenes action of receiving and sending emails through the web interface still utilizes SMTP, POP3/IMAP as relevant, but this is abstracted from the user.

In summary:

– m1: SMTP for sending emails.

– m2: POP3 or IMAP for downloading emails.

– m3: HTTP or HTTPS for checking emails in a web browser.