using System;

​

public class Program

{

    public static void Main()

    {

        var message = "Mesaj FROM: onur.... KIMDEN: ahmet";

        string[] EmailBodyStripTokens = new string[]{"FROM", "KIMDEN"};

        int TokenPosition = 0;

        foreach (string token in EmailBodyStripTokens)

        {

            if(message.IndexOf(token)>0)

            {

                TokenPosition = message.IndexOf(token);

                break;

            }

        }

        Console.WriteLine(string.Format("Ilk token posizyonu: {0}",TokenPosition));

    }

}