List of GMAIL DNS *clients*?

Occasionally one of our log analyzers will block gmail DNS requests
causing bounces when gmail claims our domain(s) are not authenticated,
they can't get to our SPF etc.

I'd like to whitelist them but does anyone know the list of IP blocks
I need?

Google has a list of IPs for their services in a JSON format available in their support section. Legitimate requests from Google should almost always come from an IP within those subnets.