SPF stands for Sender Policy Framework. It is an email authentication method used to verify if the email received is sent by a genuine sender. HubSpot recommends you to connect your email sending domain to HubSpot. But you can still add HubSpot to your DNS record by following the steps :
Creating SPF record for HubSpot:
Log in to your HubSpot account.
In the main navigation bar click on the settings icon.
Go to Website > Domains & URLs in the left sidebar menu.
Click on Advanced Options at the bottom of the page.
Click on the Copy SPF record, the SPF record will be copied to the clipboard.
Publish this record in your DNS records section for your respective domain.
Note: If you don’t have an SPF record previously for your domain, simply add “v=spf1” to the value copied from HubSpot to enable SPF for outgoing emails using HubSpot. If you do have an existing SPF record in your DNS, just update the include part of your SPF record with the value copied from HubSpot.
Wait for 24-48 hours to allow your DNS to process the changes