This article contains information on updating and validating MX records for routing inbound email through Mimecast, including prerequisites and step-by-step guidance for DNS configuration.
If you use Exchange Online as your mail provider, changing your MX records to point away from Microsoft may result in a warning message appearing under Settings > Domains within the Microsoft 365 Admin Center, stating that the record does not reflect the expected value. This warning can be safely ignored and is not inherently indicative of a mailflow problem.
Applies To
- New clients connecting with Mimecast using the Email Security Setup Wizard application.
- Customers using Mimecast for email security.
Prerequisite Tasks
Before you can modify your MX records, the following steps must be completed in your application:
- Validating Your Domains.
Walkthrough
Mail exchange (MX) records direct email to a mail server, are a resource record on the Domain Name System (DNS), and are managed via your DNS Host Provider's web interface. To validate the MX records on your domains, you must only have Mimecast's MX records and nothing else.
To route your organization's inbound email through us, you must update your mail exchange (MX) records. This designates us as the mail server responsible for accepting emails on your behalf. The process for doing this depends on your DNS hosting provider.
The following instructions are provided as a guide only.
To update your MX records:
- Log in to your DNS Hosting Account.
- Locate the page where your MX Records are maintained. You may have to enable advanced settings to access this page, which may be located under:
- DNS Management.
- Mail Server Configuration.
- Name Server Management.
- Enter the Inbound Hostnames displayed in the application into your MX records. These must be added with the same priority to ensure proper round-robin load distribution and redundancy.
- Save your change and return to the Connect Application.
- Click on the Validate button.
Any MX records found when the lookup is performed are cached for the duration specified on the domain's Time To Live (TTL). Mimecast DNS servers will respect the domain's TTL, so you'll need to wait until the cache is cleared before performing another lookup.
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