Use the information on the CNAME Records page under Settings > Hybrid Service > Hybrid Configuration to configure your DNS.
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abcdefgh is the Alias displayed on the DNS page
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mydomain.com is the Protected Domain
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CNAME indicates that you are specifying a CNAME record
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autodomain.mailcontrol.com is the Associated domain displayed with the above alias and protected domain
The above example indicates that the alias abcdefgh.mydomain.com is assigned to autodomain.mailcontrol.com. This enables the hybrid service to confirm that you own mydomain.com.
After you have created your CNAME records, click Check Status to verify that your entries are correctly set in your DNS. Resolve any error situations if necessary. If the Check Status button does not appear on the page, simply click Next to continue. If the registration process stalls or fails at this point, please see this article.
Note 
The validation performed by clicking Check Status occurs in your local system. Because the propagation of DNS changes across all Internet servers can take between a few minutes to several hours, the verification process for the hybrid service may take longer.
Click Next to continue with hybrid configuration.