[For admins] How to add a custom (original) domain to Microsoft 365

Microsoft 365 custom domain usage environment and conditions

Adding custom domains in Microsoft 365 is possible, but not available with every license.

If you want to use a custom domain, check the corresponding plan and terms of use before purchasing a license.

Exchange Online required for custom domains

In order to add a custom domain in Microsoft 365, the use of Microsoft’s corporate email service “Exchange Online” is a prerequisite.

Speaking of Microsoft, the on-premise mail server “Exchange Server” is known, but Exchange Online is a cloud-type mail service, and there is no need to install a physical server in the company.

Licenses that include Exchange Online

Some corporate licenses for Microsoft 365 come with Exchange Online, so if you want to use a custom domain, we recommend choosing from the target plans.

The mail size, the number of attachments, and the number of messages that can be sent and received are sufficient for business use.

The capacity of the mailbox and archive area varies depending on the plan, so please choose the one that suits your budget and usage scale.

*The data for each item is as of January 2023.

Data source
https://learn.microsoft.com/ja-jp/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits

License for medium-sized companies (300 people or less)

For enterprise licenses with 300 users or less, “Business Basic”, “Standard” and “Premium” plans come with “Exchange Online Plan1”.

Only the Business Premium plan can use up to 1.5TB of archive space.

License for large companies (unlimited number of people)

“Exchange Online Plan2” included in the upper plan “E3” and “E5” of licenses for large companies with no user limit can use mailbox capacity up to 100GB and has a data loss prevention function.

License for Front Workers

The exchange online entry plan “Kiosk” is attached to the licenses “F3” and “F5” for field personnel who mainly use shared terminals.

Steps to add a custom domain to Microsoft 365

After introducing Microsoft 365, let’s check the procedure to add a custom domain and set it as an email address.

Preparation

A custom domain must be prepared in advance. If you haven’t already, buy a domain first.

You can also purchase from the Microsoft 365 admin center.

Add domain to Microsoft 365 admin center

Here are the steps to add a new domain to Microsoft 365:

1. Sign in to the Microsoft 365 admin center ( https://admin.microsoft.com/ ) with an administrator account.
2. Click Settings > Domains.
3. Click Add Domain.
4. Enter the new domain and click “Use this domain”.
5. Choose a domain verification method.

Domain ownership verification

The procedure differs depending on the domain confirmation method selected in the previous section.

After verifying the domain using one of the methods below, return to the Microsoft 365 admin center and click “Continue”.

* It may take some time to reflect.

Method 1 Add a TXT record to your DNS records

Manually add the TXT record displayed on the Microsoft 365 admin center screen to your registrar’s website.

Method 2 Add MX records to your DNS records

Add MX records for registrars that do not support TXT records.

Method 3 Upload a file

Upload the text file you downloaded from the Microsoft 365 admin center to your registrar’s website.

Setting up custom domain email addresses

Once you’ve finished adding your domain, let’s give your users an email address with your custom domain.

1. In the Microsoft 365 admin center, click Users → Active Users.
2. Select the target user.
3. On the Account tab, click Manage Usernames and Email Addresses.
4. Enter the user name, select the added domain in the domain field, and click “Add”.
5. Set your custom domain email address as primary and click Save Changes.

Article Summary

Microsoft 365 allows the addition of custom domains with business licenses that include Exchange Online.

Exchange Online is a cloud-based email service, and the advantage is the convenience of being able to access it from anywhere via the Internet.

You can manage and share not only emails but also schedules and contacts on the cloud.

Switching the mail server to the cloud with the introduction of Microsoft 365 will also lead to the promotion of new work styles that are not bound by location.

NEC Networks & System Integration, which provides this article, also offers many solutions related to DX conversion and IT environments that solve corporate issues.

If you have any of these issues or concerns, please feel free to contact NEC Networks & System Integration.