What is DKIM?
DomainKeys Defined Messages (DKIM) ensures that your email contents remains trustworthy and has not been tampered with or compromised. It was originally proposed in 2007 and has been updated several times.

What is SPF?
The Sender Policy Framework (SPF) strengthens your DNS servers and restricts who can send email from your domain. SPF can prevent domains spoofing. It allows your mail server to determine when a message comes from the domain it uses. SPF has three main elements: the policy framework as its name suggests, the authentication method, and the specialized headers in the actual email that conveys this information.

Features:

FULL DKIM & SPF

PRIVATE DOMAIN 

PRIVATE IP