The vast majority of people will stick using Gmail, so aggregated metrics won't be skewed that much. However I definitely wants to mess with the fine tracking

The vast majority of people will stick using Gmail, so aggregated metrics won't be skewed that much. However I definitely wants to mess with the fine tracking like Intercom does for example, where they can pull out data about a specific client and see what communication he read or didn't read, how long he stayed on it, etc