The answer is to set the custom domain as the default domain in the Domains settings. This is correct because the default domain setting controls the domain suffix automatically applied to new user principal names (UPNs) and email addresses during user creation in the Microsoft 365 admin center. By designating contoso.com as the default, any new user will receive an email address ending with @contoso.com instead of the default @<tenant>.onmicrosoft.com. On the MS-102 exam, this question tests your understanding of identity configuration and domain management, often appearing as a straightforward scenario where you must choose between adding a domain, verifying it, or setting it as default. A common trap is confusing domain verification with setting the default—verification proves ownership but does not change the email suffix for new users. Memory tip: think of the default domain as the “stamp” for all new user addresses—change the stamp, change the output.
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 has purchased Microsoft 365 Business Premium and added a custom domain 'contoso.com' to the tenant. They want all new users to have email addresses like user@contoso.com instead of the default onmicrosoft.com domain. What should the administrator do in the Microsoft 365 admin center?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Set the custom domain as the default domain in the Domains settings.
Setting the custom domain as the default domain in the Domains settings ensures that any new user created in the Microsoft 365 admin center automatically receives an email address ending with @contoso.com instead of the default @<tenant>.onmicrosoft.com. This is the correct administrative action because the default domain setting controls the domain suffix applied to new user principal names (UPNs) and email addresses during user creation.
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.
✓
Set the custom domain as the default domain in the Domains settings.
Why this is correct
Setting a custom domain as default assigns that domain to new user email addresses automatically.
Related concept
Read the scenario before looking for a memorised answer.
✗
Add a DNS TXT record for the custom domain.
Why it's wrong here
TXT records are used for domain verification, not for setting the default email domain.
✗
Change the primary domain in the tenant's organization profile.
Why it's wrong here
The primary domain is the domain used when the tenant was created; it does not control default email for new users.
✗
Update the MX record for the custom domain to point to Exchange Online.
Why it's wrong here
MX records control mail flow, not the default email address for new user creation.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse the default domain for new users with domain verification (TXT records) or mail routing (MX records), leading them to select options that are necessary for domain setup but not for controlling the email address assigned to new users.
Detailed technical explanation
How to think about this question
The default domain setting in Microsoft 365 determines the domain suffix appended to the user principal name (UPN) and primary SMTP address when a new user is created via the admin center or Azure AD Connect. This setting does not affect existing users; it only applies to new user creation. In hybrid scenarios, the default domain must match the on-premises UPN suffix to avoid synchronization issues.
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: Set the custom domain as the default domain in the Domains settings. — Setting the custom domain as the default domain in the Domains settings ensures that any new user created in the Microsoft 365 admin center automatically receives an email address ending with @contoso.com instead of the default @<tenant>.onmicrosoft.com. This is the correct administrative action because the default domain setting controls the domain suffix applied to new user principal names (UPNs) and email addresses during user creation.
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.
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 →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company has purchased Microsoft 365 Business Standard and added the custom domain 'fabrikam.com' to the tenant. The company wants all new users to have 'fabrikam.com' as their default email domain instead of the onmicrosoft.com domain. How should the administrator achieve this?
easy
A.Update the MX record in the DNS to point to Microsoft 365 with the custom domain.
✓ B.In the admin center, go to Settings > Domains, select the custom domain, and click 'Set as default'.
C.Use the Exchange admin center to set the default email address policy to use the custom domain.
D.For each new user, manually add an email alias with the custom domain and remove the onmicrosoft.com alias.
Why B: Option B is correct because the Microsoft 365 admin center provides a dedicated setting under Settings > Domains to mark a custom domain as the default email domain. Once set as default, all new users will automatically receive a primary email address using that domain instead of the initial onmicrosoft.com domain, without requiring manual changes or additional configuration.
Variation 2. An organization has just purchased Microsoft 365 Business Standard licenses and has added the custom domain 'contoso.com' to the tenant. The administrator wants all new user email addresses to use '@contoso.com' instead of the default '@contoso.onmicrosoft.com'. How can this be achieved?
easy
✓ A.Set the default domain in the Microsoft 365 admin center to contoso.com
B.Change the primary SMTP address for each user manually after creation
C.Remove the onmicrosoft.com domain from the tenant
D.Edit the user creation PowerShell script to specify the domain
Why A: Setting the default domain to 'contoso.com' in the Microsoft 365 admin center ensures that all newly created users automatically receive an email address with the custom domain as their primary SMTP address. This is the standard method because the default domain setting controls the domain appended to new user accounts during creation, eliminating the need for manual changes.
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Question Discussion
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