The answer is that the MX record must be updated to point to Exchange Online. This is because when you add and verify a custom domain like contoso.com in Microsoft 365, inbound email routing is still governed by the existing MX record in DNS. If that record points to an on-premises mail server, any email sent to a new user created in Exchange Online will be routed to the on-premises server, which has no mailbox for that user, causing the email bounce after domain verification. On the MS-102 exam, this scenario tests your understanding of mail flow and DNS configuration, often appearing as a trap where candidates assume domain verification alone enables email delivery. A common memory tip is “verify the domain, but route the mail”—verification proves ownership, but the MX record controls delivery. To fix the bounce, update the MX record to point to Exchange Online (e.g., contoso-com.mail.protection.outlook.com). Remember: MX before mail.
MS-102 Deploy and manage a Microsoft 365 tenant Practice Question
This MS-102 practice question tests your understanding of deploy and manage a microsoft 365 tenant. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 company adds and verifies the custom domain 'contoso.com' in their Microsoft 365 tenant. However, emails sent to new users at user@contoso.com bounce back. The existing MX record for contoso.com points to the on-premises mail server. What is the most likely cause of the bounce?
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.
The domain verification failed and needs to be repeated
Why wrong: Verification is a one-time process; if verified, it remains verified. Bounces are not due to verification issues.
B
The MX record must be updated to point to Exchange Online
The MX record determines where incoming emails are sent. It must point to Exchange Online for delivery to Microsoft 365 mailboxes.
C
Users must be added to the domain in the admin center
Why wrong: Users are already assigned the domain; adding them again does not change routing.
D
The SPF record is missing or misconfigured
Why wrong: SPF records help prevent spoofing but do not affect initial email delivery; missing SPF can cause delivery issues but not outright bounces in this scenario.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The MX record must be updated to point to Exchange Online
B is correct because the MX record for contoso.com still points to the on-premises mail server. When a user is created in Exchange Online with the domain contoso.com, inbound email is routed according to the MX record. Since the MX record directs mail to the on-premises server, which does not have a mailbox for the new user, the message bounces. To deliver mail to Exchange Online, the MX record must be updated to point to Exchange Online (e.g., contoso-com.mail.protection.outlook.com).
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 domain verification failed and needs to be repeated
Why it's wrong here
Verification is a one-time process; if verified, it remains verified. Bounces are not due to verification issues.
✓
The MX record must be updated to point to Exchange Online
Why this is correct
The MX record determines where incoming emails are sent. It must point to Exchange Online for delivery to Microsoft 365 mailboxes.
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.
✗
Users must be added to the domain in the admin center
Why it's wrong here
Users are already assigned the domain; adding them again does not change routing.
✗
The SPF record is missing or misconfigured
Why it's wrong here
SPF records help prevent spoofing but do not affect initial email delivery; missing SPF can cause delivery issues but not outright bounces in this scenario.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse domain verification (a one-time DNS check) with ongoing mail routing (MX record), leading them to think verification failure is the cause, when in fact the MX record is the direct culprit.
Trap categories for this question
Scenario analysis trap
SPF records help prevent spoofing but do not affect initial email delivery; missing SPF can cause delivery issues but not outright bounces in this scenario.
Detailed technical explanation
How to think about this question
Under the hood, the MX record is the primary DNS mechanism for mail routing; it specifies the mail server that accepts email for a domain. In Microsoft 365, the default MX record target is a specific hostname like 'tenant.mail.protection.outlook.com'. If the MX record still points to an on-premises server, Exchange Online never receives the mail, and the on-premises server rejects it because no mailbox exists. A common real-world scenario is hybrid deployments where mail flow is intentionally split, but for cloud-only users, the MX record must be updated.
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 MS-102 question in full detail.
Deploy and manage a Microsoft 365 tenant — This question tests Deploy and manage a Microsoft 365 tenant — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The MX record must be updated to point to Exchange Online — B is correct because the MX record for contoso.com still points to the on-premises mail server. When a user is created in Exchange Online with the domain contoso.com, inbound email is routed according to the MX record. Since the MX record directs mail to the on-premises server, which does not have a mailbox for the new user, the message bounces. To deliver mail to Exchange Online, the MX record must be updated to point to Exchange Online (e.g., contoso-com.mail.protection.outlook.com).
What should I do if I get this MS-102 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.
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