I am currently using [forwardemail.net](https://forwardemail.net) to forward emails from my custom domain to my Gmail account. I have also set it up following their instruction to be able to send emails from my Gmail account using the custom domain.
One of the steps is to add the following DNS TXT record:
`v=spf1 a mx include:spf.forwardemail.net include:_spf.google.com -all`
Is it a potential concern in any way to have `_spf.google.com` included in the SPF record? Could anyone then easily send emails using their Gmail account with my email address without it being possible to detect in any way?