[gumby]

I don't think you need worry that your employer is watching everything you do. But they can and there are some common cases:

1 - some program is scanning ingoing/outgoing data looking for compliance violations (typically finance, some classified work; should be for medical privacy/PII but I don't see much of that happening). Also scans for liability issues such as porn at work etc. Easier to screen that stuff out up front rather than later, frankly.

2 - you have a highly restrictive job (e..g call center) and are being spot monitored from time to time; statistics are likely kept continuously. Distopian but yes, happens.

3 - Sysadmin ends up looking at some of your mail while debugging a problem or doing some investigation not necessarily related to you e.g. some employee is terminated for fraud: let's look at their correspondence, some of which -- innocently -- is from you. Or there was a disk crash and some data is being reconstructed, which includes your call logs or email or whatever.

The third case is the most common and is why there is often a blanket "we can read and get all your data" statement in the employee handbook. There are others, and you can guess them.