Sending emails programmatically, without user intervention, from an iphone application, cannot be implemented using any of the Apple frameworks. It could be possible in a jailbroken phone but then it would never see the inside of App Store.
If you want control of email sending, then a better way would be to set up a web service (at your server end) you can post to using an HTTP request. If you are posting to only one address this can work very well, although you may want to get the user to input their return mail address.
Otherwise only the standard dialog is available (this relies on using whatever account they’ve setup on the device).