Techniques are disclosed for using voicemail fingerprints to detect when a call has been answered by voicemail. A voicemail fingerprint of a known voicemail greeting is stored in association with a telephone number. The voicemail fingerprint contains a set of audio analysis streams, each of which contains audio characteristics of the known voicemail greeting beginning at a different offset from the beginning of the known voicemail greeting. A current audio analysis stream is generated containing audio characteristics of audio received beginning when a call to the telephone number is answered. If the current audio analysis stream matches one of the audio analysis streams contained in the voicemail fingerprint of the known voicemail greeting associated with the telephone number, the call to the telephone number has been answered by a voicemail box of the telephone number, and may be transferred to a secondary destination.