DomainKeys Identified Mail (DKIM) is an authentication process that verifies identities within your domain so that senders and recipients can be protected from phishing attacks and other identity spoofing:
DKIM
All of the domains that you have access to through your tenant will be listed here. You cannot edit or add domains here, but on the right-hand side, when you've highlighted a domain, you'll be given a link to enable DKIM.
If you try to enable DKIM before entering required CNAME records, you'll get an error message. Go to DNS and enter two CNAME records of the following format:
Hostname: selector1._domainkey.yourdomain.comTarget/address/value: ...
