A method and apparatus for increasing channel capacity in an Internet-based voice messaging system. Voice messages are stored in client mailboxes in the voice compression format they are received in a call answering session. During a message pickup session, the voice compression format of the retrieved message is compared to the voice compression formats or codecs supported by the user's terminal. If the voice compression format is not the same, re-negotiation is attempted, and if unsuccessful the voice message is transcoded prior to playback. If the voice compression format is the same, then the voice message is played back without transcoding. The voice message server also includes a voice prompt module which stores voice prompts in all the voice compression formats or codecs supported by the voice message server. The voice prompts are selected according to the supported voice compression format or codec and played back without the need for any transcoding.