Which protocol from the options allows a user to retrieve email from a mail server to a local mail client (mail reader)?

Introduction / Context:
Email delivery involves separate protocols for transport and retrieval. Users typically pull messages from a server to their mail client using a mailbox access protocol. This question checks recognition of the correct retrieval protocol among distractors that serve unrelated roles.

Given Data / Assumptions:

• We are considering end-user retrieval from a server to a desktop/mobile client.
• Server-side and transport protocols (for example, SMTP) are not the focus here.
• Only the listed options may be chosen.

Concept / Approach:
POP3 (Post Office Protocol version 3) is a standard mailbox retrieval protocol enabling clients to download messages from a server, often deleting or leaving copies according to settings. Another common retrieval protocol is IMAP (Internet Message Access Protocol), which syncs messages without mandatory download; however, 'IMAP' is not offered here ('MAP' is not correct). FTP is a file transfer protocol and is not used for mailbox retrieval. Therefore, among the given options, POP3 is the correct choice.

Step-by-Step Solution:

Verification / Alternative check:
Inspect a typical client configuration (for example, Outlook/Thunderbird): incoming server options are POP3 or IMAP; FTP never appears for email retrieval.

Why Other Options Are Wrong:

• FTP: Transfers files, not email messages from mail stores.
• MAP: Not a valid mail retrieval protocol; likely a misspelling of IMAP.
• All of the above: Cannot be correct since FTP and 'MAP' are invalid for mail retrieval.
• None of the above: Incorrect because POP3 is valid.

Common Pitfalls:
Confusing transport (SMTP) with retrieval (POP3/IMAP) and assuming any network file protocol can retrieve mailboxes.

Final Answer:
POP3