sircodAccording to the specifications here http://support.creative.com/kb/ShowArticle.aspx?sid=123379 there are no 4-pole headset jacks - it works as a headphone OR a mic jack, not both. I've also opened up the unit and confirmed that it's a 3-pole jack. It's a pity.
KrisLyssaraPerhaps to accommodate sources which merge line out and mic into one output and to allow it to be used for either audio out and mic in. Though the E3 only uses one or the other and not both, sadly
acupperI asked their support department for clarification. This is what they had to say:
"The E3 has two 3,5mm jacks to connect your headphone: one headphone out and one headphone out/mic in. Both jacks can handle 4-pole connectors but only the combined headphone/mic jack can handle audio and mic simultaneously. So in case you have a 4-pole TRRS connector (headphone with mic), you can just plug the device to the headphone/mic jack and you can have audio output and mic input. The other headphone jack only can handle audio, so the mic will not work."