Question: Can any one please let me know why the sagepay throws the 5006 (Unable to redirect to Vendor's web site.), i can able to post transaction to sagepay and can able to give credit card information at sagepay's end. But, my problem is once it return back to my notification page it throws error 5006.

and i could not reach my success or fail URLs at my end.

Answer: 
Try

* <https://support.sagepay.com/forum/Topic10228-29-1.aspx>
* <https://support.sagepay.com/forum/Topic11245-21-1.aspx>

for some ideas. Just search their forum for 5006. There is plenty posts.

As a general advice: with Payment Gateways it is usually better to ask for support at their respective vendors sites.
The RedirectURL is usually a page hosted on your own site which is designed to be an order complete page that we redirect the shopper's web browser to upon transaction completion. 

For more information on this, please check [Sage Pay Server Protocol and Integration Guidelines](https://www.google.com/search?q=Sage%20Pay%20Server%20Protocol%20and%20Integration%20Guidelines).