Which protocol is NOT typically used for email retrieval?

The protocol used for email retrieval typically involves standards that are specifically designed for accessing and managing email messages on a mail server. In this context, the correct answer relates to HTTP, which is primarily a protocol for transferring web pages and other resources on the internet.

While protocols like POP3 and IMAP are specifically tailored for retrieving messages from a mail server, SMTP is used for sending emails from a client to a server or between servers, not for retrieving messages. HTTP, although it can be utilized for accessing web-based email platforms (such as Gmail or Yahoo Mail), does not function as an email retrieval protocol in the traditional sense, where emails are directly downloaded or managed via a dedicated email client.

In essence, while HTTP is essential for web traffic, it does not serve the specific role of retrieving emails in the way that POP3 and IMAP do. Therefore, HTTP stands out as the correct choice that does not belong to the category of protocols typically used for email retrieval.