How can users access their voicemail messages using the IPO system?

Users can access their voicemail messages in the IPO system through multiple methods, which is why the correct answer includes a variety of options. Specifically, users can listen to their voicemail directly on their phone by dialing into the voicemail system, receive notifications via email that contain voicemail messages, and access messages through the Voicemail Pro web interface. This flexibility allows users to choose the method that best suits their preferences and circumstances.

By providing these varied access methods, the IPO system enhances user convenience and ensures that messages are easily reachable, regardless of whether the user is at their desk, on the go, or away from their phone. The inclusion of different access points promotes effective communication and ensures that important messages are not missed.