SPF/DKIM is necessary for Email Service Providers to properly authenticate the emails we're sending on your behalf. This ensures deliverability of the emails from Stamped.io to your customers.
The DNS records are usually added to the Domain Registrar (e.g. GoDaddy, Namecheap, etc).
Here are the CNAME DNS records to add:
CNAME Record #1
CNAME Record #2
CNAME Record #3
Once the records are added, do email firstname.lastname@example.org and we will need to validate the records