The email should be received, filtered, and put into a database with an index. If any information escapes this database, outside of going to the user's email client, then we have a privacy problem with google "reading" the mail.
This definition isn't perfect but it should be enough for to you understand the intent.
I'm far too jaded to be "upset" or even "disappointed" that, whenever they have a way to do so, Google reads everything that everyone sends to each other. But perhaps it seems perfectly normal and ok to you that a third party reads what should be private communications. Perhaps "private" isn't even a thing for some.
This definition isn't perfect but it should be enough for to you understand the intent.