CRAM-MD5 Authentication -- Please answer this mail

Hi Friends..

Now i somehow managed to build my CRAM-MD5 algorithm..
but still am getting failure notice in authentication from the server

Please do spare some minutes for me and consider this sample case:

Username : vijayan(_at_)test123
Password : vijayan123


Server's Response for AUTH CRAM-MD5 : "PDEzMTcwMTY1MjguOTM2MzU4OEB0ZXN0MTIzPg=="
(greeting or secret)

then I made Base64 decode string (Challenge): 
<15703(_dot_)1133435409(_at_)server(_dot_)jataayusoft(_dot_)com>


then the md5 algorithm formed the digest on this buffer which is
digest = "08efc84630335743ec35966c80b23c5a"

so the full base64 decoded string is : "vijayan(_at_)test123 
08efc84630335743ec35966c80b23c5a"

now i made the base64 encode on this string, which returns
"dmlqYXlhbkB0ZXN0MTIzIDA4ZWZjODQ2MzAzMzU3NDNlYzM1OTY2YzgwYjIzYzVh"


this buffer i sent to server. But the server return "535 authentication failed 
(#5.7.0)



pls check these sequences and letme know where the error occured..
is my algorithm is correct..??

if any error where it might be..?

pls help in this..

hope to get a reply from anyof u regarding this issue..

thanks in advance,
Vijayan