from what i've read, ALL email ( possible 0.000something tolerance/error ) goes through google's mail-transfer-agents.
If they want a copy of every email that goes across the internet, they've got the saturation-of-core-servers to have that.
There simply isn't any way to bypass that.
on an irrelated note, i wish public key encryption had been normalized, & worked right..
( Snowden got stung by a misconfiguration, 1 time, & if geeks get stung, then it isn't ready for normals )
🙏