Emailing from within Unity iPhone or Android

Is it possible to interface with email -- whether native on the device, or some built-in protocol to send email in Unity?

Its possible but you will need to write own plugins to do so to use the platforms native functionality for it, Unity does not hook up any such functionality. I think Prime31 has such a plugin and the Unity EP from Bliprob contains such functionality as well.

The mailapi is rather simple, its a matter of a single function to get the view to show, let the user feed the data and send it. You can prefill the mail if required

Should be able to use the .NET smtp classes, e.g. http://msdn.microsoft.com/en-us/library/system.net.mail.smtpclient.aspx

If they don't work, you could use WWW (from the Unity API) to send to a webserver, which creates and sends the email