The correct answer is username@<tenantname>.onmicrosoft.com. This format is the default email address for new users because when a company signs up for Microsoft 365 Business Standard without adding a custom domain, Microsoft automatically provisions a default domain in the structure of <tenantname>.onmicrosoft.com. Every user account created in this tenant is assigned an email address using that onmicrosoft.com domain until a custom domain is verified and added. On the MS-102 exam, this concept tests your understanding of initial tenant provisioning and domain management; a common trap is assuming a custom domain is required for user creation, but the exam emphasizes that the default email format without custom domain is always the tenant’s .onmicrosoft.com suffix. To remember this, think of the tenant name as the unique identifier—just like a street address before you add a house number—so the pattern is always username@tenantname.onmicrosoft.com.
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 just signed up for Microsoft 365 Business Standard without adding a custom domain. An administrator needs to create the first user accounts. What will be the default email address format for these new users?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
username@<tenantname>.onmicrosoft.com
When a Microsoft 365 tenant is created without adding a custom domain, the default domain is the `<tenantname>.onmicrosoft.com` domain. New user accounts are automatically assigned an email address in the format `username@<tenantname>.onmicrosoft.com`, as this is the initial domain provisioned for the tenant. Option C correctly reflects this default behavior.
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.
✗
username@contoso.com
Why it's wrong here
The custom domain has not been added yet, so it cannot be used as the default email suffix for new users.
✗
username@onmicrosoft.com
Why it's wrong here
This is close, but the domain name includes the org's prefix. Unless the org name is 'onmicrosoft', this is incorrect.
✓
username@<tenantname>.onmicrosoft.com
Why this is correct
By default, new users get email addresses using the initial domain, which is tenantname.onmicrosoft.com.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
username@microsoftonline.com
Why it's wrong here
microsoftonline.com is not used for user email addresses; it is the authentication endpoint domain.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the default `onmicrosoft.com` domain with the generic `microsoftonline.com` domain used for Azure AD authentication, or assume a custom domain like `contoso.com` is automatically assigned, leading them to select A or D instead of recognizing the tenant-specific subdomain format.
Detailed technical explanation
How to think about this question
Under the hood, when a Microsoft 365 tenant is created, Azure AD provisions a default domain in the format `<tenantname>.onmicrosoft.com`. This domain is used for all user principal names (UPNs) and email addresses until a custom domain is added and verified via DNS TXT or MX records. The UPN format follows RFC 5321 and 5322 standards, and the tenant name is derived from the initial sign-up (e.g., the organization name or a unique identifier). In a real-world scenario, if an administrator later adds and verifies a custom domain like `fabrikam.com`, they can change the default email domain for new users, but existing users retain their original `onmicrosoft.com` addresses unless explicitly 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: username@<tenantname>.onmicrosoft.com — When a Microsoft 365 tenant is created without adding a custom domain, the default domain is the `<tenantname>.onmicrosoft.com` domain. New user accounts are automatically assigned an email address in the format `username@<tenantname>.onmicrosoft.com`, as this is the initial domain provisioned for the tenant. Option C correctly reflects this default behavior.
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: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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