Remember! Your boss can read your emails (on Gmail)
Nobody likes to be spied upon, especially when the person spying is none other than your own boss! We know, this sounds like a petty (and mean) thing to do, but the fact is, your boss can indeed look into your mail if you're using the corporate email account provided by them. In other words, an account on G Suite product, Gmail. Here's how.
Companies use G Suite for providing work collaboration, communication tools
The Gmail we use for our personal emails is the consumer version that Google offers free. But, beyond this one, there is also an enterprise version of Gmail, which comes as a part of G Suite - the batch of paid corporate tools that companies use for giving their employees access to basic computing, productivity and collaboration tools.
G Suite products other than Gmail
In addition to Gmail, G Suite products include Hangouts, Calendar, and Currents for communication; Google Drive for storage; Docs, Sheets, Slides, Keep, Forms, and Sites for productivity and work collaboration.
G Suite admins have the ability to access your activity
While G Suite tools make work easier, it's important to note that the admin of G Suite can access individual account activity for any of their products. Now, this means your boss has the ability to look at everything you may be doing in their G Suite-backed Google products, including Gmail. So, essentially, they could even check the drafts you may have saved.
Other data can also be accessed
Along with Gmail, companies can also access the data on your other G Suite products, like the file you may have saved or shared with a colleague using Drive. The level of access could vary according to the G Suite plan taken by your company, but Google has clearly said that it is always possible for them to check your data.
Here is Google's official stance on data access
"It's important to note that your administrator has access to any data you store in this account, including your email," Google says about the case of data access on its G Suite account permissions help page.