The hackers who broke into HBO’s internal networks weren’t able compromise the network’s email system, HBO President and CEO Richard Plepler told staff in an internal email Wednesday.

“Many people have expressed particular concern about our e-mail system,” he wrote. “At this time, we do not believe that our e-mail system as a whole has been compromised, but the forensic review is ongoing.”

Earlier this week, news broke that hackers had broken into the company’s computer networks and possibly stolen as much as 1.5 terabyte of data. The hackers proceeded to leak unreleased episodes of a handful of shows, and promised to leak more data in the coming days. A security contractor hired by the company revealed in a filing Tuesday that “thousands of internal documents” were stolen as part of the hack.

Plepler’s email was apparently meant to calm the nerves of the network’s staff, and address what he called “an enormous amount of speculation in the media.” “It is important to understand that, as is often the case, things you read may very well not be true,” he wrote.

However, it’s worth noting that the hackers may have been able to get their hands on at least some internal communication even if they were not able to break into the company’s email servers. As part of the leak, hackers also published a list of account user names and passwords of a senior executive Monday. At least one of these accounts could have been used to give them access to that person’s corporate email correspondence.

Plepler also wrote Wednesday that HBO was working with an outside firm to provide free credit monitoring for its employees, suggesting that personal information of employees may have been part of the leak. He ended his email by asking employees to “continue to do the excellent work which defines this company across all departments and know that the appropriate teams are working round the clock to manage our way through this difficult period.”