- A
Port 25
Why wrong: Port 25 is SMTP, used for sending; if sending works, this port is open.
- B
Port 110
Port 110 is the default port for POP3, used for receiving email; if blocked, incoming mail fails.
- C
Port 443
Why wrong: Port 443 is HTTPS, used for secure web traffic, not for email receiving.
- D
Port 53
Why wrong: Port 53 is DNS, used for name resolution, not for email.
Question 990 of 1,020
220-1201 Network Protocols Practice Question
This 220-1201 practice question tests your understanding of network protocols. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A user reports that they can send emails but cannot receive any. The email client is configured with SMTP for outgoing and POP3 for incoming. The server is reachable. Which port is most likely blocked on the firewall for the incoming mail protocol?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
✓
Port 110
The user can send emails (SMTP works) but cannot receive them, and the incoming protocol is POP3. POP3 uses port 110 by default. Since the server is reachable, a firewall blocking port 110 would prevent the email client from retrieving incoming messages, while SMTP on port 25 remains unaffected.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Port 25
Why it's wrong here
Port 25 is SMTP, used for sending; if sending works, this port is open.
- ✓
Port 110
Why this is correct
Port 110 is the default port for POP3, used for receiving email; if blocked, incoming mail fails.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Port 443
Why it's wrong here
Port 443 is HTTPS, used for secure web traffic, not for email receiving.
- ✗
Port 53
Why it's wrong here
Port 53 is DNS, used for name resolution, not for email.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CompTIA often tests the distinction between SMTP (port 25) and POP3 (port 110) by describing a scenario where only one direction of email flow is broken, leading candidates to mistakenly focus on the outgoing port.
Detailed technical explanation
How to think about this question
POP3 (Post Office Protocol version 3) operates over TCP port 110 for unencrypted connections, while POP3S uses port 995 for SSL/TLS. The client connects to the server, issues commands like USER, PASS, LIST, and RETR to download emails. A firewall blocking port 110 would cause the client to time out or receive a connection refused error, even though SMTP on port 25 works fine.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 220-1201 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Network Protocols — study guide chapter
Learn the concepts, then practise the questions
- →
Network Protocols practice questions
Targeted practice on this topic area only
- →
All 220-1201 questions
1,020 questions across all exam domains
- →
CompTIA A+ Core 1 220-1201 study guide
Full concept coverage aligned to exam objectives
- →
220-1201 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Related 220-1201 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Mobile Device Hardware Servicing practice questions
Practise 220-1201 questions linked to Mobile Device Hardware Servicing.
Mobile Device Connection Methods practice questions
Practise 220-1201 questions linked to Mobile Device Connection Methods.
Mobile Device Accessories practice questions
Practise 220-1201 questions linked to Mobile Device Accessories.
Mobile Device Network Connectivity practice questions
Practise 220-1201 questions linked to Mobile Device Network Connectivity.
Mobile Device Application Support practice questions
Practise 220-1201 questions linked to Mobile Device Application Support.
Network Protocols practice questions
Practise 220-1201 questions linked to Network Protocols.
TCP & UDP Ports practice questions
Practise 220-1201 questions linked to TCP & UDP Ports.
Wireless Networking Technologies practice questions
Practise 220-1201 questions linked to Wireless Networking Technologies.
Network Services practice questions
Practise 220-1201 questions linked to Network Services.
Network Configuration Concepts practice questions
Practise 220-1201 questions linked to Network Configuration Concepts.
Common Networking Hardware practice questions
Practise 220-1201 questions linked to Common Networking Hardware.
IP Addressing practice questions
Practise 220-1201 questions linked to IP Addressing.
Practice this exam
Start a free 220-1201 practice session
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
Questions learners often ask
What does this 220-1201 question test?
Network Protocols — This question tests Network Protocols — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Port 110 — The user can send emails (SMTP works) but cannot receive them, and the incoming protocol is POP3. POP3 uses port 110 by default. Since the server is reachable, a firewall blocking port 110 would prevent the email client from retrieving incoming messages, while SMTP on port 25 remains unaffected.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Keep practising
More 220-1201 practice questions
- During a network cable installation, a technician needs to verify that a newly run Cat6 cable is properly terminated and…
- A user connects a 4K monitor to their laptop using a USB-C port. The monitor is detected, but the resolution is stuck at…
- A technician is troubleshooting a laptop that will not charge. The battery is removable, and the power adapter works on…
- A customer brings in a smartphone with a broken charging port. They want the port replaced. During disassembly, the tech…
- A user reports that their laptop's keyboard types random characters when certain keys are pressed. The laptop has not be…
- A technician is troubleshooting a laptop that shuts down randomly after a few minutes of use. The fan is spinning, and t…
Last reviewed: Jul 4, 2026
This 220-1201 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 220-1201 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.