I'm sure there are other solutions, but one of the simplest would be to have the user click an e-mail link in a public contact directory... assuming a limited number of inbound callers where you already know the e-mail address associated with that caller. In this case, clicking the e-mail link would open a new message in the user's default mail application.
If the e-mail interaction needs to be handled through Interaction Center, then a custom handler solution would likely be required.