Microsoft 365 Certified: Administrator ExpertDeploy and manage a Microsoft 365 tenantMedium
A Microsoft 365 E3 tenant has a custom domain 'contoso.com'. The administrator wants to ensure that all internal email communication sent from users in 'contoso.com' to other users in 'contoso.com' is never subject to external spam filtering or routing delays. Which DNS record type, if misconfigured or missing, would most likely cause internal email to be routed externally before being delivered internally?
- AA record
- BMX record
- CTXT record
- DCNAME record
Show answer & explanationAnswer & explanation
Correct answer: B. MX record
The MX (Mail Exchanger) record specifies the mail servers responsible for accepting email messages on behalf of a domain. If the MX record for 'contoso.com' points to an external server (or is missing/incorrect), internal emails might be routed out to the internet, processed by external spam filters, and then routed back into the organization, leading to delays and unnecessary external exposure.
Why the other options are wrong
- A. A records map hostnames to IP addresses, primarily for web traffic, not email routing.
- C. TXT records provide text information and are used for verification (like SPF/DKIM for email validation), not for directly routing email.
- D. CNAME records create aliases for domain names and are used for various services but not the primary determinant of email routing.
DNS MX Record
A DNS record that specifies the mail servers responsible for accepting email messages on behalf of a domain name.
- Essential for email delivery.
- Contains a priority value to indicate preference for multiple mail servers.
- Must point to the correct mail server (e.g., Exchange Online) for proper email flow.
Memory trick: Think of the MX record as the post office address for your domain's email.