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220-1201 Practice Question: That their email client can receive messages but…
A user reports that their email client can receive messages but cannot send any. The email server settings are correct, and the user can connect to the internet. The firewall is blocking outbound traffic on certain ports. Which protocol and port combination is likely blocked?
⚠ Common exam trap
The 220-1201 exam often tests the distinction between incoming (POP3/IMAP) and outgoing (SMTP) mail protocols, trapping candidates who confuse receiving ports with sending ports.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
SMTP on port 25
SMTP (Simple Mail Transfer Protocol) is used for sending outgoing email messages. By default, SMTP uses port 25. If the firewall blocks outbound traffic on port 25, the email client can still receive messages (using POP3 or IMAP) but will be unable to send any, perfectly matching the user's symptoms.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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POP3 on port 110
Why it's wrong here
POP3 (Post Office Protocol version 3) on port 110 is exclusively used for retrieving email from a mail server to a client. When a client connects via POP3, it typically downloads messages to the local device and may delete them from the server. Therefore, blocking port 110 would prevent the user from receiving new emails, but it would have no impact on their ability to send outgoing messages, as sending uses a different protocol.
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IMAP on port 143
Why it's wrong here
IMAP (Internet Message Access Protocol) on port 143 is another protocol dedicated to email retrieval, allowing clients to access and manage messages directly on the mail server. Unlike POP3, IMAP synchronizes mailboxes across multiple devices, keeping messages on the server by default. Blocking this port would prevent the user from accessing their inbox and receiving new mail, but it would not affect the separate process of sending emails.
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SMTP on port 25
Why this is correct
SMTP (Simple Mail Transfer Protocol) on port 25 is the standard protocol specifically designed for sending email messages between mail servers and from an email client to an outgoing mail server. If port 25 is blocked, the email client would be unable to establish a connection with the server to transmit outgoing messages. This would directly prevent the user from sending emails, while their ability to receive mail via POP3 or IMAP would remain unaffected.
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HTTPS on port 443
Why it's wrong here
HTTPS (Hypertext Transfer Protocol Secure) on port 443 is primarily used for secure communication over a computer network, most commonly for secure web browsing. While webmail interfaces utilize HTTPS for secure access, blocking this port would impact general internet access and secure website connections, not the specific underlying protocol (SMTP) used by a dedicated email client for sending messages. Email clients use distinct ports for their sending and receiving functions.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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