How to Add a Second Custom Domain to Your Microsoft 365 Tenant
A company has an existing Microsoft 365 tenant with the verified custom domain 'contoso.com'. The administrator now wants to add a second custom domain, 'contoso-europe.com', to the same tenant. What is the first step the administrator should take?
Quick Answer
The correct first step is to add the domain in the Microsoft 365 admin center. This action is essential because the admin center generates a unique TXT verification record that must be placed in the public DNS zone of the new domain, proving ownership before any services can be configured. On the MS-102 exam, this question tests your understanding of the domain verification workflow, which is a foundational task for hybrid and multi-domain environments. A common trap is assuming you can directly update DNS records or add users first, but without initiating the domain addition in the admin center, you won’t have the specific verification token required. Remember the sequence: Admin Center first, then DNS record, then verification. A helpful memory tip is “Add to Admin, then add to DNS”—the admin center always generates the key you need to prove you own the second custom domain.
⚠ Common exam trap
A common mix-up: candidates assume the first step is to create a DNS record (like TXT or MX) directly, but the correct sequence requires initiating the domain addition in the admin center first to obtain the necessary verification value.
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 in the Microsoft 365 admin center.
The first step to add a second custom domain to an existing Microsoft 365 tenant is to initiate the domain addition process in the Microsoft 365 admin center. This triggers the system to generate the unique TXT verification record that must be added to the public DNS zone to prove ownership of the domain. Without first adding the domain in the admin center, the administrator would not know the specific verification value required for the DNS record.
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 in the Microsoft 365 admin center.
Why this is correct
Adding the domain in the Microsoft 365 admin center is the first step, which generates the required TXT or MX verification record. Only after DNS verification succeeds can the administrator create users, mailboxes and configure services for contoso-europe.com.
- ✗
Add a TXT verification record in the public DNS zone for 'contoso-europe.com'.
Why it's wrong here
A TXT record proves ownership, but it is created after the domain is entered in the Microsoft 365 admin centre, which generates the unique verification value. Publishing TXT first is tempting because it is the visible verification artefact, yet the wizard must supply the token beforehand.
- ✗
Add an MX record pointing to Exchange Online in the public DNS zone for 'contoso-europe.com'.
Why it's wrong here
MX records route mail and are configured only after the domain is verified and added to the tenant; publishing one first does nothing. MX configuration is tempting because mail flow is the goal, but it belongs to the DNS-validation stage that follows domain verification, not the initial step.
- ✗
Contact Microsoft support to enable the domain addition feature.
Why it's wrong here
Adding custom domains is self-service in the Microsoft 365 admin centre; no support involvement is required. Contacting support is tempting when a tenant setting appears restricted, but the portal permits multiple verified domains by default, so the administrator simply starts the add-domain wizard.
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Key term
Microsoft 365 tenant
A Microsoft 365 tenant is a dedicated, isolated instance of Microsoft 365 services created for an organization when they sign up for a subscription.
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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Variation 1. Your company is deploying Microsoft 365 for a new subsidiary with 500 users. You need to configure the initial tenant with a custom domain (contoso.com) and verify ownership. What is the first step you must perform?
easy- A.Delegate the contoso.com zone to Microsoft 365 DNS servers.
- B.Create user accounts with the custom domain before verification.
- ✓ C.Add a TXT record provided by Microsoft 365 to the contoso.com DNS zone.
- D.Set contoso.com as the default domain in the Microsoft 365 admin center.
Why C: To verify ownership of a custom domain in Microsoft 365, you must prove you control the domain's DNS zone. Microsoft provides a unique TXT record value that you add to the public DNS zone of contoso.com. Once the TXT record propagates, Microsoft queries it and confirms ownership, allowing you to proceed with domain configuration.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.