[Email DLP] Add a Domain to an Existing DKIM

Description

This article explains how to apply DKIM to new domains for customers who have already configured DKIM for Email DLP and are adding new domains for use.
* For information on adding domains for use, please refer to the following article.
I want to add a domain for use

Notes

1. The content of this article is based on the product specifications as of June 2026 and may be changed without notice.
2. Administrator role for Email DLP is required to view the actual screens or make configuration changes.
   For instructions on how to access the administration, please refer to the following article.
   [Email DLP] How to log in to the administration
3. If you want to enable DKIM records for multiple domains, including subdomains (e.g., sub.example.com), please add the TXT record to the DNS of all target domains.
   * You can also refer to the TXT record registered in the main domain using a CNAME record.
   For more details, please refer to the following article.
   [Email DLP] If you are using multiple domains, do you need to register the DKIM public key for all domains?

Procedure

1. In the Email DLP administration, select [Tenant Settings] - [DKIM], and click the [Settings] link.
   * If DKIM has not been configured, please refer to the following article.
   [Email DLP] Tenant Settings - DKIM Configuration

   

2. Add the displayed values to the TXT record in the DNS of the domain you are adding.
   You can copy the TXT record name and value by clicking the copy button displayed to the right of each.
   * By default, the tag "t=y;" (Test Mode) is included in the TXT record value. If you are using this for actual training, uncheck [Include test mode tag (t=y;)] before copying.
   * If you want to enable DKIM signatures for multiple domains, including subdomains (e.g., sub.example.com), you need to add this TXT record to the DNS of each target domain.
   You can also refer to the TXT record registered in the main domain using a CNAME record.
   For more details, please refer to the following article.
   [Email DLP] If you are using multiple domains, do you need to register the DKIM public key for all domains?

   

3. Open Command Prompt (Windows) or Terminal (Mac OS), run the command, and confirm that the value of the TXT record you set is displayed.

   For Windows OS (run in Command Prompt)

   nslookup -type=TXT <selector name>._domainkey.<added domain> 8.8.8.8

   [Example Output]

   C:\Windows\system32>nslookup -type=TXT <selector name>._domainkey.<added domain> 8.8.8.8
   Server: dns.google
   Address: 8.8.8.8
   
   Non-authoritative answer:
   <selector name>._domainkey.<added domain>. text =
   "v=DKIM1; k=rsa; t=y; p=MIGfMA0GCSqGSIb3<omitted>dPx4QIDAQAB"

   For Mac OS (run in Terminal)

   dig +short @8.8.8.8 <selector name>._domainkey.<added domain> txt

   [Example Output]

   dig +short @8.8.8.8 <selector name>._domainkey.<added domain> txt
   "v=DKIM1; k=rsa; t=y; p=MIGfMA0GCSqGSIb3<omitted>dPx4QIDAQAB"

4. After registering the TXT record, return to the [Tenant Settings] - [DKIM] settings in the Email DLP administration, and click [Settings] for the selector in use.

   

5. Enter the new domains, separated by line breaks.

   

6. Click the [Apply] button.