Why don’t you use voice recognition? - About Speaking Email
A study by a University of South Carolina psychology researcher found that planning to speak and speaking put far more demands on the brain's resources than listening. We've found ourselves personally that trying to get voice recognition systems to take commands can be big distraction. Actually tapping the phone quickly (and usually without looking) seems to require much less attention than the fully hands free approach of talking to an app.
In some places though, voice control is the only legal way to interact with an app while driving. So it may be a feature that we add in future if we get many requests for it (email us firstname.lastname@example.org).
Part of the problem is that voice recognition does not work very well while the phone is speaking. We could pause for voice input at the end of an email, but ideally you would want to interrupt Speaking Email by saying “archive” or “next” in the middle of an email being spoken. If an incorrect recognition triggers a command to archive an email, it can be a pain. We would rather have an app that does what it does really well than include a feature that has “issues”.