How do I send an email on IOS using Application.OpenURL with more than one line of body text?

Did you try double-escaping the backslashes? Something like:

 Application.OpenURL ("mailto:someone@gmail.com?subject=EmailSubject&body=Email\\r\\nBody");

Or maybe you need to use HTML URL encoded entities.

 Application.OpenURL ("mailto:someone@gmail.com?subject=EmailSubject&body=Email%0D%0ABody");

Take also a look at C# verbatim string literals:

 @"first line blabla
 second line thingy."

You have to encode the url inorder to open it .Use the below link for encoding and decoding http://meyerweb.com/eric/tools/dencoder/

%0A%0D

For your example:

Application.OpenURL ("mailto:someone@gmail.com?subject=EmailSubject&body=Email%0A%0DBody");

Made up a little dynamic function off the Unity API which will 'smart escape' your url without messing with the root domain; enjoy.

  public static string SmartEscapeURL(string url) {
         
             string escapedArgs = "";
             string[] parts = url.Split('?');
             if (parts.Length == 1) return url;
             string[] args = parts[1].Split('&');
             for (int i = 0; i < args.Length; i++) {
                 string[] kvp = args[i].Split('=');
                 if (kvp.Length == 2) {
                     escapedArgs += String.Format("{0}={1}", 
                         WWW.EscapeURL(kvp[0]).Replace("+", "%20") , 
                         WWW.EscapeURL(kvp[1]).Replace("+", "%20"));
                     if (i < args.Length - 1) escapedArgs += "&";
                 }
             }
 
             string eUrl = parts[0] + "?" + escapedArgs;
             return eUrl;
         }

Isaac