- A
Add the domain to the safe sender list in the user's Outlook client.
Why wrong: This only affects that user and still may be filtered by server-side rules.
- B
Add the domain to the allowed sender list in the anti-spam policy.
Why wrong: This bypasses all spam filtering for that domain.
- C
Disable anti-phishing protection for the affected users.
Why wrong: This would remove protection for all emails.
- D
Create a mail flow rule to set the Spam Confidence Level (SCL) to -1 for emails from that domain.
This allows the email but still scans for malware and phishing.
Question 426 of 985
Defender for Office 365 Allowlisting
This MS-900 practice question tests your understanding of describe microsoft 365 apps and services. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: spam Confidence Level (SCL). 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 company deploys Microsoft Defender for Office 365 to protect against phishing. Users report that legitimate external emails are being moved to Junk Email folder. The security team needs to allowlist a specific sender domain without reducing protection. What should they do?
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
✓
Create a mail flow rule to set the Spam Confidence Level (SCL) to -1 for emails from that domain.
Option D is correct because creating a mail flow rule to set the SCL to -1 for emails from the specific domain prevents those messages from being processed by spam filtering while still allowing anti-phishing and other security checks to apply. This ensures legitimate external emails are delivered to the inbox without reducing the overall protection provided by Microsoft Defender for Office 365. Unlike Options A and B, which either are ineffective client-side or reduce protection by bypassing filtering for the entire domain, Option D maintains full security for all other senders.
Key principle: Spam Confidence Level (SCL)
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 the domain to the safe sender list in the user's Outlook client.
Why it's wrong here
This only affects that user and still may be filtered by server-side rules.
- ✗
Add the domain to the allowed sender list in the anti-spam policy.
Why it's wrong here
This bypasses all spam filtering for that domain.
- ✗
Disable anti-phishing protection for the affected users.
Why it's wrong here
This would remove protection for all emails.
- ✓
Create a mail flow rule to set the Spam Confidence Level (SCL) to -1 for emails from that domain.
Why this is correct
This allows the email but still scans for malware and phishing.
Related concept
Spam Confidence Level (SCL)
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap is that candidates may think setting the SCL to -1 bypasses all security filtering, but in reality it only bypasses spam filtering. Anti-phishing protection continues to scan these messages for malicious links or attachments, so security is not reduced. Also, candidates might confuse mail flow rules (server-side) with user-level safe sender lists, which do not affect server-side filtering.
Detailed technical explanation
How to think about this question
The SCL value ranges from -1 (skip filtering) to 9 (highest spam confidence). A mail flow rule (transport rule) can set SCL to -1 for messages matching specific conditions, such as sender domain, which overrides all subsequent filtering including anti-phishing and anti-spam policies. This approach is granular and reversible, allowing administrators to whitelist a domain without creating a blanket exception in the anti-spam policy, which would also disable URL detonation and spoof intelligence for that domain.
KKey Concepts to Remember
- Spam Confidence Level (SCL)
- Mail flow rule
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
Spam Confidence Level (SCL)
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. Spam Confidence Level (SCL) Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Review spam Confidence Level (SCL), then practise related MS-900 questions on the same topic to reinforce the concept.
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FAQ
Questions learners often ask
What does this MS-900 question test?
Describe Microsoft 365 apps and services — This question tests Describe Microsoft 365 apps and services — Spam Confidence Level (SCL).
What is the correct answer to this question?
The correct answer is: Create a mail flow rule to set the Spam Confidence Level (SCL) to -1 for emails from that domain. — Option D is correct because creating a mail flow rule to set the SCL to -1 for emails from the specific domain prevents those messages from being processed by spam filtering while still allowing anti-phishing and other security checks to apply. This ensures legitimate external emails are delivered to the inbox without reducing the overall protection provided by Microsoft Defender for Office 365. Unlike Options A and B, which either are ineffective client-side or reduce protection by bypassing filtering for the entire domain, Option D maintains full security for all other senders.
What should I do if I get this MS-900 question wrong?
Review spam Confidence Level (SCL), then practise related MS-900 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Spam Confidence Level (SCL)
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Last reviewed: Jun 24, 2026
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