If you give an App access to your emails (and other data) it should come as no surprise that they use the access. And sometimes that could mean humans reading emails contents, and possibly not for the expected reason. Here are ways to check who has access to your data in Google and Microsoft.com and how to remove the access.
Click on an item to see what access it has, you then have an option to remove access.
Click on Edit to see what access it has, you then have an option to remove access