It's a reality that has some people sweating— app developers have access to private Gmail Accounts.
According to the Verge, it's rather common for developers in the third-party category to be able to read the contents of people's Gmail accounts, specifically those who use the email service's app. It was also said that they can analyze the contents of the email account.
Now, before you lose your mind, you have to know that Google has some strong vetting procedures in place to ensure this isn't taken advantage of. A company like Google is sure to have only the most trustworthy of developers with these privileges, so it's likely only a tiny portion of app developers who can, in fact, see private emails.
Some of the vetting procedures are a manual review, automated review, and testing of the app's homepage to ensure that it is a real app that's helping users instead of stealing their information.
Obviously, Google is very safe with data and would not want to cause any harm to their customer base. Think about it, Google has always cared about their users and continue to do so, that's why they have put these protective procedures in place and been rather honest with everyone in the wake of the information coming out.
The other lesson is to always read the user agreement. Those who did read it probably wouldn't be surprised this was happening at all.
While we do expect our emails to be secure, it's obvious that almost anything on the internet is not. Maybe we'll stick to the good old-fashioned pen and paper to get in touch with our loved ones from now on.