LPIC-2 DNS, Web and Mail Services Practice Question
A Postfix administrator wants to restrict which clients can relay mail through the server. Which three smtpd restriction lists are typically used for this purpose? (Choose three.)
⚠ Common exam trap
Test-takers frequently confuse `smtpd_sender_restrictions` with relay control, but it only filters based on the sender address, not on whether the client is authorized to relay mail.
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
✓
smtpd_helo_restrictions
A is correct because `smtpd_helo_restrictions` allows the administrator to enforce checks based on the HELO/EHLO hostname presented by the client during the SMTP greeting. By using restrictions like `reject_invalid_helo_hostname` or `reject_non_fqdn_helo_hostname`, the server can block clients that provide suspicious or non-compliant HELO names, which is a common tactic to prevent unauthorized relay attempts.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
smtpd_helo_restrictions
Why this is correct
Checks the HELO/EHLO hostname.
- ✗
smtpd_data_restrictions
Why it's wrong here
Checks message data, not relaying.
- ✗
smtpd_sender_restrictions
Why it's wrong here
Used for sender verification, not relaying decisions.
- ✓
smtpd_client_restrictions
Why this is correct
Controls which clients can connect.
- ✓
smtpd_recipient_restrictions
Why this is correct
Primary list for relaying decisions.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.