In my case, I had these spam-invites sent from my G Suite email to my personal Gmail. I could see the emails on the Sent folder.
The weird part is that I had a strong password (1password) + 2-factor on both accounts. I use FF with containers so I only use my email on a container and nowhere else.
I had reviewed all the 3rd party apps and security settings on both accounts and it all looked normal to me. The only issue is that I didn't had the SPF, DMARC and DKIM setup - fixed after it.
The weird part is that I had a strong password (1password) + 2-factor on both accounts. I use FF with containers so I only use my email on a container and nowhere else.
I had reviewed all the 3rd party apps and security settings on both accounts and it all looked normal to me. The only issue is that I didn't had the SPF, DMARC and DKIM setup - fixed after it.
I sent email to abuse@google but got no response.