Update SPF record so Netlify Forms can send on behalf of custom domain

I have my domain name hosted with an external provider and I have Outlook (Office 365) set up with my domain name.

I have configured the domain name so non-www (apex) and www URLs point to my Netlify-hosted site.

What do I add to my SPF record so Netlify Forms can send emails as well as Outlook? Or is it not required?

My SPF is a typical Outlook 365 TXT record:
"v=spf1 include:spf.protection.outlook.com -all"

hi spanners,

i think there might be something useful in here: