A. Mail Host
B. Mail Server
C. Content Mixing System
D. Email Server

Solution

B. Mail Server

Explanation

Mail access starts with the client when the user needs to download email from the mail server. The mail server stores incoming emails for each user until they are retrieved by the client's email application (such as Outlook, Thunderbird, or a web-based client like Gmail). When a user initiates the process to check their email, the client application connects to the mail server, authenticates the user, and downloads any new emails that have been received since the last time the client checked for mail.