MS-102 Deploy and manage a Microsoft 365 tenant Practice Question
A Microsoft 365 administrator needs to add a new verified domain named tailspintoys.com to the tenant and then configure it as the default domain for new user principal names. Which sequence of actions should the administrator perform in the Microsoft 365 admin center?
⚠ Common exam trap
The trap here is reversing the order and assuming the default designation can be applied before Microsoft verifies DNS ownership of the domain.
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
✓
Add the domain, create the required TXT or MX verification record at the DNS host, verify ownership, then set the domain as default.
Adding a custom domain requires proving DNS ownership through a TXT or MX record generated by the admin center. Only after verification succeeds can the domain be marked as default, which controls the suffix applied to new user principal names and email addresses. Setting default first, pre-creating records, or attempting account-based verification all fail because Microsoft requires DNS proof before the namespace is usable.
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, verify it by signing in with a global administrator account from that domain, then set it as default.
Why it's wrong here
Domain verification relies on a DNS record such as a TXT or MX entry, not on authenticating with an account in the new namespace, which cannot exist until the domain is verified. Signing in with a global administrator does not prove DNS ownership and will not complete the verification step.
- ✗
Set the domain as default first, then add the verification TXT record so Microsoft can confirm ownership afterward.
Why it's wrong here
A domain cannot be designated as default until Microsoft has verified ownership, because the tenant must prove control before it can use the namespace. Attempting to set default first is not possible in the admin center workflow and would leave the domain in an unverified state where it cannot host mailboxes.
- ✓
Add the domain, create the required TXT or MX verification record at the DNS host, verify ownership, then set the domain as default.
Why this is correct
Adding a domain in the Microsoft 365 admin center generates a verification record that must be published at the public DNS provider. After Microsoft confirms the record, ownership is verified and the domain can be designated as the default, which makes it the suffix used for new user principal names and new email addresses.
- ✗
Create the verification record at the DNS host, then add the domain and set it as default in a single step.
Why it's wrong here
The admin center must generate the specific verification value for the tenant before the record can be published, so creating a record in advance is not feasible. Even if a record existed, the domain still must be added and verified through the portal before the default designation becomes available.
Visual reference
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Related to this question
Learn chapter
Custom Domain Management in Microsoft 365
Key term
Microsoft 365
Microsoft 365 is a subscription-based cloud service from Microsoft that combines productivity tools like Office apps with security, device management, and online storage.
Key term
Custom domain
A custom domain is a personalized internet address (like contoso.com) that you can use with cloud services instead of the default domain provided by the service provider.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Microsoft exam blueprint
This MS-102 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the MS-102 exam.