Yeah, I fell into that rabbit hole once. Tried all abuse channels that I could find. network-abuse@ refers you to the Google Cloud abuse form. They ‘are not able to take action on this report since the IP mentioned in the report is not hosted on Google Cloud.’ Gmail abuse doesn’t even bother to reply (why should they, it’s not about Gmail after all). In the end, I just blocked DKIM identifiers related to Firebase via Rspamd.
replyYou can try: https://support.google.com/mail/contact/abuse?hl=en
replyI submitted an account that sent phishing emails last week, but I’m told it’s basically a black hole and to not expect anything anything to happen.
It's not gmail accounts, but "services" (?) hosted on Google's cloud. Basically I see X.X.X.X.bc.googleusercontent.com addresses in the "Received" header fields, e.g. "22.185.141.34.bc.googleusercontent.com"
replyWhen doing a WHOIS on that IP we'll get a contact address for abuse reports: "google-cloud-compliance@google.com", but sending anything there, returns an error that the user doesn't exists.