I want to ensure that DKIM has been set.
Go to Protocols/Domains/ and select the domain of your choice for which You would like to set DKIM. Refer to DomainKeys Identified Mail section and provide all necessary data following the documentation.
As soon as DNS records will be populated double check by executing the command shown below:
nslookup -type=TXT [Selecotor]._domainkey.[domain] [DNS IP binded to your SMG]