Since FoxyCart is (usually) sending your customers their email receipt, you probably want to disable Authorize.net's email receipt. In “Settings” → “Email Receipts”, uncheck the checkbox under “Enable Email Confirmation”.
Once you're set up your Authorize.net gateway you really should review your AVS settings. It's in Settings → Address Verification Service.
Make sure you at least give this a look when using Authorize.net. Many non-US banks don't support AVS, and Authorize.net's default settings reject cards from banks that don't support it. This may not be the behavior you want, so please make sure you understand what all the information on this page means. If you leave it as is, you'll likely be rejecting many international orders.
If you're not a high-risk target for fraudulent orders you can uncheck most of the checkboxes. Many merchants leave “B” as the only box checked and don't have issues, though checking B, E, R, and N is probably a good idea. Every business is different so we recommend exploring the settings and only checking the boxes you want checked. Keep an eye on your store's error log to catch problems and adjust your AVS settings to resolve them, if necessary. If you anticipate many international orders you'll likely want to relax the AVS settings significantly. More on Authorize.net's FAQ.
If you are a high-risk target for fraud, or you're experiencing a lot of it, you probably want to check B, E, R, U, S, and N, and give serious consideration to G.
From your “Settings” page, click the “Card Code Verification” link under “Security Settings”, and make sure all the checkboxes are unchecked. If you need to check any of these options, please ensure that you understand that FoxyCart's may sometimes send transactions without the CSC. More information is on the payment gateway overview page.
Make sure you check whether or not your Authorize.net account is configured to require the customer phone number. If it is, you'll need to make that a required field on your checkout: http://wiki.foxycart.com/faqs#can_i_make_customer_phone_a_required_field
You can use the default FoxyCart Authorize.net Test Server account for testing (in your “Payment Gateway” settings), but this won't allow you to see all the transaction details on the backend. Select the “Test Server” radio button, then check the checkbox to use the default values.
If you'd like to set up your own test Authorize.net account, set it up here. Select the “Test Server” radio button in your “payments” page in your FoxyCart admin, then use your own test server API ID and transaction key.
You can also test with your live account. Choose the “Live Server” radio button in the FoxyCart admin, enter your real API ID and transaction key, and save. Then go to your Authorize.net account and enable test mode there.
While you're using a Test Authorize.net Server you can run test transactions using the test card number 4111111111111111, with any expiration date in the future and any 3 digit CSC number.
Response Reason Codes and Response Reason Text is the authoritative source for descriptions and explanations of Authorize.net reason response codes.
Be sure to review your AVS settings, as they may be overly restrictive by default for merchants doing international transactions.
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