fd.findElement(By.id("SignUp_Id")).sendKeys("testing01@abc.com");
fd.findElement(By.id("SignUp_password")).sendKeys("test123");
    fd.findElement(By.id("submit")).click();

for(int count=1; count < 10; i++){
    fd.findElement(By.id("SignUp_Id")).sendKeys("testing" + i + "@abc.com");
    // Rest of the script
}