The use of DKIM (DomainKeys Identified Mail) usually improves deliverability. DKIM and SPF (Sender Policy Framework) are the most applied methods to authenticate senders.

The establishment of DKIM for a sender domain provides a digital signature in the header of all emails that are sent with the sender's domain on promio-connect. With this signature the recipient can validate the identity of the sender by matching with a public key, and thus verify the authenticity of the e-mail sender.

For sender domains of promio-connect setting up DKIM is mandatory.