MS-102 Deploy and manage a Microsoft 365 tenant Practice Question
Your organization has a Microsoft 365 tenant with a custom domain contoso.com. You have configured Exchange Online to accept emails for contoso.com. You now need to add a subdomain sales.contoso.com and ensure that email sent to sales.contoso.com is delivered to a specific shared mailbox. What should you do?
⚠ Common exam trap
Candidates often confuse adding a subdomain as a custom domain (which requires unnecessary DNS verification) with adding it as an accepted domain in Exchange Online, which is the correct approach for routing email to a specific mailbox without altering the parent domain's verification status.
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 sales.contoso.com as an accepted domain in Exchange Online and create a transport rule to redirect emails to the shared mailbox.
To route email for a subdomain to a specific mailbox, you must first add the subdomain as an accepted domain in Exchange Online (not as a custom domain in the admin center, since the parent domain is already verified). Then, you create a transport rule that matches recipients in that accepted domain and redirects the messages to the target shared mailbox. This ensures that all emails sent to sales.contoso.com are delivered to the designated mailbox without requiring additional MX records or domain verification.
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 sales.contoso.com as a custom domain in the Microsoft 365 admin center and verify ownership.
Why it's wrong here
Adding sales.contoso.com as a custom domain in the Microsoft 365 admin center is unnecessary and administratively heavy. Subdomains are not registered as separate custom domains; they are configured in Exchange Online as accepted domains. Even if you added it and verified DNS, that alone would not route mail to the shared mailbox; you would still need a mail flow rule. Furthermore, registering it as a custom domain would require adding the subdomain to your tenant and verifying DNS, which can interfere with UPN or email address policies.
- ✓
Add sales.contoso.com as an accepted domain in Exchange Online and create a transport rule to redirect emails to the shared mailbox.
Why this is correct
This is correct because an accepted domain in Exchange Online tells the service to accept email addressed to that domain (or subdomain). To make the subdomain deliverable, you must add sales.contoso.com as an accepted domain with the 'Internal Relay' or 'Authoritative' type. Then, a transport rule (mail flow rule) can be configured to match any recipient in that subdomain and redirect the message to the sales shared mailbox. This ensures all mail sent to @sales.contoso.com lands in the shared mailbox without needing separate mailboxes.
- ✗
Configure an auto-expanding archive for the shared mailbox.
Why it's wrong here
Auto-expanding archiving is a mailbox storage feature that automatically adds additional archive storage when the user's archive mailbox reaches its limit. It does nothing to affect inbound email routing or the acceptance of messages from a subdomain. Enabling this on a shared mailbox would only expand its archived storage capacity, not allow sales.contoso.com to send emails to it. Therefore, it has no relevance to the requirement.
- ✗
Create a distribution group named sales@contoso.com and add the shared mailbox as a member.
Why it's wrong here
Creating a distribution group with the address sales@contoso.com is incorrect because it uses the parent domain, not the sales.contoso.com subdomain, and it would not cause Exchange Online to accept messages for that subdomain. Without an accepted domain configuration for sales.contoso.com, mail sent to any address at that subdomain will be rejected as nonexistent. Even if a group named sales@contoso.com existed, the organization still needs to configure the subdomain as an accepted domain and apply a transport rule to route or forward mail to the shared mailbox.
Go deeper
Related to this question
Learn chapter
Exchange Online Protection and Anti-Phishing
Key term
Mailbox
A mailbox is a storage location on a mail server where incoming and outgoing email messages are kept for a user or group.
Key term
Domain verification
Domain verification is the process of proving that you own or control a specific domain name so that you can use it with a service like Microsoft 365.
About these practice questions
One of 712 original MS-102 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.