Have you read my email?

During Tuesday's class we talked a little bit about whether or not it is ethical to monitor or read the emails of a board member suspected of leaking company insider information. I have some experience reading one of my employee's emails in my last job. The employee was in a manager position and was having a lot of difficulty with her job--she was unable to complete her tasks or manage her staff. Her staff kept reporting that she was spending all day on her work computer doing personal emails and shopping online. I put her on a performance improvement plan and spent several months coaching her. The amount of time and effort put into improving her was due in part to the fact that she'd been working in the department for several years and had been successful in previous assignments. Additionally, she was part of an employee union, making letting her go very difficult. Ultimately, after much effort, it was determined that we were not going to be able to convert her to a productive employee and she was unwilling to step down into a lesser role like the one she'd been successful in before. It was time to let her go. Although I'd been diligent in keeping records of both her failures and our attempts toward improvement, upper management and the school district lawyers wanted additional proof of her incompetence. For this, they asked that we prove that despite multiple warnings, she was still using her work computer for personal emails and Internet surfing during business hours. The district wasn't set up to monitor this easily, so I had to go into the system at the employee's location and manually go through her old emails (sent and received). Doing this ended up proving that her behavior had not changed since the start of her PIP. Because we could prove that this behavior had not changed, there was more credibility in the eyes of the lawyers to the documentation I had regarding the lack of change in other areas and I was able to let the employee go. Was this ethical? I believe that it was because the email address assigned to our onsite managers was not a personal email account. Our onsite managers had a generic email assigned to their location, not to them personally. Additionally, they were informed that email monitoring was a possibility. We only did this when there was a recognized need to do so and only after clearing it with the attorney first. The personal information that the employee was writing about in her emails was not shared with anyone other than myself and my boss. However, even though I feel like this was an ethical thing to do, it is definitely something that I had to think twice about before I came to that decision. It was in no way cut and dry--which is how most "is it ethical" debates are, not cut and dry.