IMAP (Internet Message Access Protocol) is the correct answer because it allows users to access their email from various devices while keeping emails on the server. This means that changes made on one device (like reading an email or moving it to a folder) will be reflected on all devices. POP3 (Post Office Protocol 3), on the other hand, typically downloads and potentially removes the email from the server, which could prevent access from other devices. HTTP/S (Hypertext Transfer Protocol/Secure) is for accessing web pages, not specifically designed for email retrieval. SMTP (Simple Mail Transfer Protocol) is used for sending emails, not for syncing and reading emails across multiple devices.