DomainKeys Identified Mail
DKIM is a method which allows the receiving e-mail server to cryptographically determine the identity of the system behind the e-mails and treat it accordingly. Ubivox uses the DKIM system to identify ourselves, and all e-mails leaving Ubivox are signed using our DKIM keys.
This technique is amongst others recognized by Yahoo! Mail, Gmail, and Fastmail and often results in quicker dispatching of the received e-mails.
An added bonus from the cryptografic signature is that all of the important headers (e.g. subject and sender/recipient) is bound by the signature. This means that the recipient can be sure that the mail was not altered during transport.