No changes are required to your domain's SPF record to use Envoke.
SPF is used to validate the "envelope" address on an email message. This address is distinct from the "from" address displayed to recipients. All messages sent through Envoke use an Envoke envelope address, and we manage the SPF record for its domain. This means you can send messages through Envoke, using your own domain in the "from" address, without adding Envoke's servers to your SPF record.