I used this to determine that Xfinity was compromise, yet still no acknowledgement despite reporting the issue to them and they went through some spiel about ho

I used this to determine that Xfinity was compromise, yet still no acknowledgement despite reporting the issue to them and they went through some spiel about how I received the email by mistake and continue to receive emails by mistake at <randomword>_<randomword>@<customdomain>. The only person I shared that email with was them, and never had the issue with another provider.