The correct action is to add a 'Block sender' action in Microsoft Defender for Office 365, as this is the native mechanism within Automated Investigation and Response (AIR) to block a sender email address across all mailboxes. This works because the action adds the sender to the tenant’s tenant-level block list, which is enforced at the transport layer for all inbound email, effectively preventing delivery from that address to any mailbox in the organization. On the SC-200 exam, this question tests your understanding of where specific remediation actions live—many candidates mistakenly look for a “block sender” action in Defender for Endpoint or Azure AD, but the key is that email-level blocking is always handled by Defender for Office 365 playbooks. A common trap is confusing a manual mailbox rule with an automated AIR action; remember that AIR actions are policy-driven and global. Memory tip: “Block the sender, not the device—think Office 365 for email, Endpoint for files.”
SC-200 Manage a security operations environment Practice Question
This SC-200 practice question tests your understanding of manage a security operations environment. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Your security team is investigating an incident in Microsoft Defender XDR where a user received multiple phishing emails. The team needs to create an automated response that blocks the sender's email address across all mailboxes in the organization. Which action should you configure in an automated investigation and response (AIR) playbook?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a 'Block sender' action in Microsoft Defender for Office 365.
Option C is correct because blocking a sender's email address across all mailboxes is a native capability of Microsoft Defender for Office 365. The 'Block sender' action in an AIR playbook directly adds the sender to the tenant's block list, which is enforced at the transport layer for all inbound email, effectively preventing any further delivery from that address.
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.
✗
Add a 'Block IP address' action in Microsoft Defender for Cloud Apps.
Why it's wrong here
Incorrect. Defender for Cloud Apps blocks IPs, not email senders.
✗
Create a custom detection rule in Microsoft Sentinel.
Why it's wrong here
Incorrect. Sentinel can detect but not directly block email senders.
✓
Add a 'Block sender' action in Microsoft Defender for Office 365.
Why this is correct
Correct. This action blocks the sender across Exchange Online.
Related concept
Read the scenario before looking for a memorised answer.
✗
Deploy a configuration profile in Microsoft Intune.
Why it's wrong here
Incorrect. Intune manages devices, not email senders.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the scope of Microsoft Defender for Cloud Apps (Option A) with email security controls, mistakenly thinking IP blocking in MDCA can stop email from a specific sender, when in fact email transport blocking is handled exclusively by Defender for Office 365.
Detailed technical explanation
How to think about this question
The 'Block sender' action in Defender for Office 365 leverages the Exchange Online tenant allow/block list, which is stored in the Exchange Online organization configuration and enforced by the transport pipeline (specifically the Connection Filtering and Content Filter agents). This action is idempotent and applies globally within minutes, overriding user-level junk mail settings. In a real-world scenario, if the phishing campaign uses multiple sender addresses from the same domain, you would need to block the domain rather than individual addresses, which is also supported via the same action.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this SC-200 question in full detail.
Manage a security operations environment — This question tests Manage a security operations environment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a 'Block sender' action in Microsoft Defender for Office 365. — Option C is correct because blocking a sender's email address across all mailboxes is a native capability of Microsoft Defender for Office 365. The 'Block sender' action in an AIR playbook directly adds the sender to the tenant's block list, which is enforced at the transport layer for all inbound email, effectively preventing any further delivery from that address.
What should I do if I get this SC-200 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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