Sign in to your domain account at your domain host (not your Google Admin console).
Go to the page for updating your domain's DNS records.
This page might be called something like: DNS management, name server management, or advanced settings.
Find your TXT records and check if your domain has an existing SPF record.
The SPF record starts with "v=spf1".
If your domain does not have an SPF record, add a TXT record with these values:
Name/Host/Alias: @ (or don't enter anything)
Other DNS records for your domain might indicate the correct entry.
Time to Live (TTL): 3600 or leave the default.
Value/Answer/Destination: v=spf1 include:_spf.google.com -all
If your domain does have an existing SPF record, add the following to it:
Do not create another SPF record.
Save the record.
Your new SPF record takes effect within 48 hours.