I\'m using the MFMailComposeViewController to send an email from within an iPhone v3.0 application. I programmatically create the message body text and display it before sho
If you are referring to the signature in the iPhone Simulator, it's just there by default. There's no Mail.app and therefore no settings for Mail to disable it. You can't actually send an email either, but it's just nice that they at least enabled MPMailComposeViewController. If you use MFMailComposeViewController, the user's signature on their own device will display in the bottom of your custom app message.
As far as I know, this is a global mail setting that can be specified by the user. By default the signature is set to "Sent from my iPhone", but it can be changed in Settings - Mail,Contacts,Calendars - Signature