http://www.911software.com/credit_c...PN_Compliance#Which_merchants_are_affected.3F How to implement AMEX CAPN with Authorize.net Gateway?
This only applies to businesses using Amex split dial or Reverse PIP. If you're using Authnet, split dial and reverse PIP are not an issue for you. These two options are only available to retail merchants, and of all retail businesses only about 1/1000 are using them.