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TechKnowSurge Catalog Interactives Which Mail Agent Does This?
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Which Mail Agent Does This?

Follow Sally's email to Bob and name the part of the mail system that does each step.

⚑ Complete this interactive to capture a CTF flag worth 5 points.

About this interactive

Sally (sally@domain.com) writes an email to Bob (bob@example.com) in her mail client, the mail user agent (MUA). When she clicks Send, the client hands it to the mail submission agent (MSA) configured in her settings, the first stop in the mail system. From there it goes to a mail transfer agent (MTA), a mail relay. There may be one relay or many. The sending MTA looks up example.com's MX record in DNS to find the receiving MTA, and SMTP pushes the message from relay to relay, assuming each next server is up. The last MTA passes it to the mail delivery agent (MDA), which stores it. It has to wait there, because Bob's machine may be off. When Bob opens his own MUA, the client retrieves his mail with IMAP or POP3, since SMTP can only push. The MSA, MTA and MDA may be separate machines or one box, depending on the setup. By default none of these protocols encrypt anything, which is why the next lessons add security.

What you'll learn

Aligned to

CompTIA Security+
4.5 Given a scenario, modify enterprise capabilities to enhance security.
2.2 Explain common threat vectors and attack surfaces.

Key terms

Mail User Agent
MUA
The client-side software that allows a user to compose, send, and receive email messages.
Mail Submission Agent
MSA
A server component that receives outgoing email from a mail user agent and forwards it to a mail transfer agent for delivery.
Mail Transfer Agent
MTA
A server component responsible for relaying email messages between mail servers using SMTP.
Mail Delivery Agent
MDA
The component that receives email from a mail transfer agent and stores it in the recipient's mailbox until retrieved.
Simple Mail Transfer Protocol
SMTP
A TCP-based application-layer protocol used to send email messages between mail servers and from mail clients to outbound mail servers, typically on port 25 (server-to-server) or port 587 with TLS (client submission). SMTP only handles sending mail; retrieval is handled by separate protocols such as IMAP or POP3.

Topics

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