Creating / Modifying your SPF record for increased deliverability
Openfax highly recommends that all customers using both EBS or AirMail implement an SPF record that specifies Openfax mail relay servers as authorized senders for the customers domain.
More support details available at:
What is SPF?
SPF or Sender Policy Framework is an electronic mail standard that helps to control forged e-mail. It allows domain owners a way to specify legitimate sources for mail from their domain. It uses a TXT record specified in a domain’s DNS server to accurately specify allowed senders. You can learn more about SPF by visiting the OpenSPF Project.