In the latest twist in the saga of Greg Smith’s very public departure from Goldman Sachs Group, Reuters reports that the firm is now scouring the company’s internal email in search of the word “muppet.”

In his New York Times op-ed attacking his former employer, Smith alleged that his coworkers there fobbed off bad investments on clients and insulted their intelligence. In particular, he said the firm’s managing directors referred to their clients as muppets—British slang that refers not to Jim Henson’s creations but to stupid people.

The Reuters story reports that the company is reviewing Smith’s allegations, in part by scanning internal emails. That action should serve as a reminder for office workers that nothing they communicate electronically from the office is their private business.

By now, most employees are probably well aware that it’s inadvisable to send an application for a new job on office email or visit inappropriate websites on a company computer. Back in 2007, the American Management Association found that 66 percent of employers monitored their Internet connections and a full 28 percent had fired a worker for inappropriate email use.

But Goldman Sachs’ actions show that workers need to watch what they type even if they’re pretty sure their boss wouldn’t bat an eye at what they’re saying. If a company comes under scrutiny for any reason, there’s a good chance someone will dig into all interoffice communication. Sometimes, it’s an internal investigation like Goldman’s. Other times it’s a political thing—like the way reporters dug through the largely mundane emails from Sarah Palin’s time as governor of Alaska when they were released last year.

The biggest worry for most companies is that they’ll end up in some kind of legal dispute and have an aggressive lawyer wading through their internal emails. They may even get an IT: Azure/AWS consulting company to help pull out messages that the sender and recipient thought had been permanently deleted.

Even failing to archive old messages can be dangerous in a legal battle because it might suggest that the company was trying to hide something.

The question of what to keep out of official business communication can become even more complicated when employees use company laptops or smartphones, or even when they use their own mobile devices for work purposes. Social media also blurs lines since it can be easy to lose track of whether a Twitter handle is a work tool or a vehicle for personal expression.

As with most things, it’s always a good idea to be cautious. At most companies, the best practice is probably to use email for uncontroversial work topics. Off-topic conversation, jokes and—especially—rants about a situation that’s causing problems should be saved for the water cooler or the bar after work.

And if you feel an urge to call a client a muppet, it’s probably a good time to just bite your tongue. After all, that’s what Kermit would do.