Sendinblue is a third party sender based in France:

Aligned Authentication method:

SPF - Yes - Only if the customer has a dedicated IP

DKIM - Yes TXT record

With a dedicated IP, the customer will configure a dedicated subdomain for Sendinblue. This can either be hosted on the customer’s DNS or the subdomain can be delegated to Sendinblue.

Sendinblue has a verification process that checks to see if a customer has correctly published SPF and DKIM records before they will send in an aligned way.

Sendinblue does a simple text match for their SPF include and is not able to recognize the  Valimail Macros. They have the ability to bypass this behind the scenes

More information is available here: