We implemented AIM method with the Authorize.Net Payment Gateway long time ago.
Basically, we would send the x_password in the post data to the Authorize.Net Payment Gateway.
We found some situation that recently created account cannot succeed the transaction and got the response reason code 103 - This transaction cannot be accepted.
Until we removed x_password from the post data to the Payment Gateway, the transaction became approved.
So, does the AIM method have any policy changed on x_password?
Could you please give us some suggestion about it?
Thank you very much.
I don't know what it may have been in the past, but you're supposed to send x_login and x_tran_key, neither of which are your account password. You may want to download a recent version of the SDK and start over with your code.
(if using PHP, look for a file called AIM.markdown in the doc folder for sample code)
You can also look here for documentation: