SPF
To authorize Paubox to send emails on your behalf you will have to include it in your SPF record. The SPF record mechanism used by Paubox is shown below.
include:_spf.paubox.com
For more information on SPF please click on the button below.
DKIM
Paubox do not seem to support DKIM at the moment but please reach out to their support team for more up to date information.