LPIC-2 DNS, Web and Mail Services Practice Question
This LPIC-2 practice question tests your understanding of dns, web and mail services. 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 systems administrator is configuring a Postfix mail server to use Dovecot for SASL authentication. The authentication method is set to PLAIN in Dovecot, and Postfix has smtpd_sasl_auth_enable=yes and smtpd_sasl_type=dovecot. Dovecot's auth socket is at /var/run/dovecot/auth-client. The mail logs show repeated "SASL authentication failed" errors for known good credentials. The administrator checks that the socket exists and that Dovecot is running. What is the most likely cause?
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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The postfix user does not have read permission on the Dovecot auth socket.
The most likely cause is that the Postfix user (typically 'postfix' or the mail queue owner) lacks read permission on the Dovecot auth socket at /var/run/dovecot/auth-client. Dovecot's SASL authentication via a Unix socket requires the connecting process (Postfix) to have read/write access to that socket file. Even though the socket exists and Dovecot is running, if the permissions are too restrictive (e.g., owned by 'dovecot' with mode 0600), Postfix cannot communicate with Dovecot's auth service, resulting in repeated 'SASL authentication failed' errors despite valid credentials.
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.
✗
The smtpd_recipient_restrictions does not include permit_sasl_authenticated.
Why it's wrong here
This would cause relay rejection after authentication, not authentication failure.
✗
The Dovecot service is not listening on TCP port 143 for IMAP.
Why it's wrong here
Dovecot's SASL service uses a Unix socket, not IMAP port.
✗
The mynetworks parameter in Postfix is set incorrectly.
Why it's wrong here
mynetworks controls relaying, not authentication.
✓
The postfix user does not have read permission on the Dovecot auth socket.
Why this is correct
The socket file permissions may restrict access to the postfix user, causing authentication failures.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a running service and existing socket guarantee functionality, overlooking Unix socket permissions and the need for the Postfix process user to have read/write access to the auth socket.
Detailed technical explanation
How to think about this question
Dovecot's SASL authentication for Postfix uses a Unix domain socket (typically /var/spool/postfix/private/auth or /var/run/dovecot/auth-client) where the socket's permissions must allow the Postfix user (often 'postfix' or 'nobody') to connect. In many distributions, Postfix runs in a chroot jail under /var/spool/postfix, so the socket path must be mapped accordingly (e.g., /var/spool/postfix/private/auth). A common real-world scenario is forgetting to add the postfix user to the dovecot group or failing to set the socket mode to 0660, which silently breaks authentication.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
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.
DNS, Web and Mail Services — This question tests DNS, Web and Mail Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The postfix user does not have read permission on the Dovecot auth socket. — The most likely cause is that the Postfix user (typically 'postfix' or the mail queue owner) lacks read permission on the Dovecot auth socket at /var/run/dovecot/auth-client. Dovecot's SASL authentication via a Unix socket requires the connecting process (Postfix) to have read/write access to that socket file. Even though the socket exists and Dovecot is running, if the permissions are too restrictive (e.g., owned by 'dovecot' with mode 0600), Postfix cannot communicate with Dovecot's auth service, resulting in repeated 'SASL authentication failed' errors despite valid credentials.
What should I do if I get this LPIC-2 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 →
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.
This LPIC-2 practice question is part of Courseiva's free LPI 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 LPIC-2 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.