If your domain manager is Register.com, please follow the below steps.

1. Login to your Register.com account
2. Under My Domains, select the domain name you have added in Zoho for verification.
3. Scroll down to the Advanced Technical Settings section and click Edit Domain Aliases.
4. Go to Text (TXT records) and click Edit TXT Records.
5. Enter the details for your TXT record. 
   • In the Host field, enter @ ​
   • In the TXT Value field, enter the TXT value generated in the Zoho Mail Admin Console
   • In the TTL field, enter 3600 seconds
6. ​Click Continue.
7. Click Save Changes.
8. Now come back to mailadmin.zoho.com page and click 'Verify by TXT'.
9. If the DNS information is correctly propagated, the domain will be verified. You can proceed with the next steps to create user accounts. 

If your domain manager is Register.com, please follow the below steps.

1. Login to your Register.com account
2. Under My Domains, select the domain name you have added in Zoho for verification.
3. Scroll down to the Advanced Technical Settings section and click Edit Domain Aliases.
4. In the field to the left of .yourdomain.com, specify the zb*******, the code generated in Zoho for verification.
5. In the Points to field, specify the value from the CNAME Value/ Points To/ Destination field of your Zoho Mail Admin Console and select Continue.
6. In the next page, verify the entries you have added and click Continue to create the CNAME Records. 

You have now added the CNAME successfully. You may have to wait for at least an hour for the changes to take effect in the DNS Servers. After an hour or two, log in to your Zoho Mail control panel and click Verify. Once your domain is verified, you can start adding users and creating mail accounts.

If your DNS is hosted with Register.com, follow the instructions below to change the MX Record of the domain and receive emails.

1. Login to your Register.com account.
2. Under the My Domains and Services, select the domain for which you want to change the MX records.
3. Scroll down to the Advanced Technical Settings section and Click Edit MX records.
4. Leave the Host Name field blank, select 'High' from the priority drop down. 
5. Specify mx.zoho.com. in the Mail Server field. 
6. Select add another record with priority as low and MX records as mx2.zoho.com.
7. Select add another record with priority as low and MX records as mx3.zoho.com.

   The MX values given above are based on the generic configuration information. For more specific configuration particular for your domain refer this section in the Admin Control Panel.

   Note:

   The dot(.) at the end of the MX record is optional. This depends on your DNS provider. We recommend you to go through your DNS providers support documentation for the exact method to add the MX entries.

8. In case you have MX entries of old servers, remove the records to receive emails in Zoho without any errors. 

Once saved, you have added the MX records in your Register.com DNS. You can check the propagation of MX records using Zoho's MX record checker tool. When you provide the domain name in the tool, the MX records of Zoho Mail should be returned as the result. In case you have difficulties adding the MX entries, you can get the assistance of Register.com support, to update the MX records of your domain.