Zimbra – Add DKIM to domain

DKIM is an email authentication method that uses a digital signature to let the receiver of an email know that the message was sent and authorized by the owner of a domain.

To enable DKIM on your domain with Zimbra you will need to use the zmdkimkeyutil utility

sudo su zimbra

/opt/zimbra/libexec/zmdkimkeyutil -a -d mydomain.com

You can then take the output from this command to add a new TXT record in your DNS

DKIM Data added to LDAP for domain mydomain.com with selector 395E1A58-F8DF-11EE-8184-68CFF6C3E978
Public signature to enter into DNS:
395E1A58-F8DF-11EE-8184-68CFF6C3E978._domainkey IN      TXT     ( "v=DKIM1; k=rsa; "
          "p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3+BdAWkwwMCZnWXpauGdGeuf7ounnxS7xIY721B99Dgpu487LcYmIU2G65ZdFwzkKSBChSt2YqQHre8LINQhsbnUjBQkpQ6aiuMPm9UeQMkLw6PMPoJoac0E9mUJBmffgKPOG/AETnc2r82vjmJVgQ8i+txQYVX8SQlPzLq5cmIElg//h53R9qJcJCpabH37rfJ5R+N0mnjlDG"
          "oDiWUi/yfnmSPohwidjYmYqj/RIcIEqbayg88Yo4fhsExHgIVTBb/6c2JLoYc/uGtRp07uqj/pTbMWdnUvP8D56nmsNwhhz23hG6p9zR//nfZArZsUJdH+V+6veC8/RLw/75QkSwIDAQAB" )  ; ----- DKIM key 395E1A58-F8DF-11EE-8184-68CFF6C3E978 for mydomain.com

In our case the TXT Record name is:

395E1A58-F8DF-11EE-8184-68CFF6C3E978._domainkey

The content of the record is:

v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3+BdAWkwwMCZnWXpauGdGeuf7ounnxS7xIY721B99Dgpu487LcYmIU2G65ZdFwzkKSBChSt2YqQHre8LINQhsbnUjBQkpQ6aiuMPm9UeQMkLw6PMPoJoac0E9mUJBmffgKPOG/AETnc2r82vjmJVgQ8i+txQYVX8SQlPzLq5cmIElg//h53R9qJcJCpabH37rfJ5R+N0mnjlDGoDiWUi/yfnmSPohwidjYmYqj/RIcIEqbayg88Yo4fhsExHgIVTBb/6c2JLoYc/uGtRp07uqj/pTbMWdnUvP8D56nmsNwhhz23hG6p9zR//nfZArZsUJdH+V+6veC8/RLw/75QkSwIDAQAB

Ref: https://wiki.zimbra.com/wiki/Configuring_for_DKIM_Signing