Since we now are able to reply back to voice messages if the sender filled out the form with his or her email address, then you could potentially have a back-and-forth conversation with others via speakpipe. Currently, the inbox is not suited for organizing conversations of this nature. The inbox and sent messages pages provide some organization, however, it creates an unnatural segmentation. If you wanted to recall the whole conversation, you would need to go back an forth between the inbox and the sent messages pages and keep track of the message IDs in the process. Support for threaded conversations as we see in Gmail would be ideal - particularly for teaching speaking, listening, and interactive fluency in the field of the teaching and learning a second language.