Besides Domainkeys and DKIM, SPF record is also a popular method for email authentication. It is recommended to setup SPF record for your domain.
Setup of SPF record is simple, which only requires to deploy a TEXT record in your domain DNS server. Please refer to the following url for details. http://www.openspf.org/
If you have any problem in DomainKeys/DKIM/SPF record implementation, please contact support@emailarchitect.net.