I'm interested in a solution which handles the transaction on Authorize.net's servers but afterwards posts back to Salesforce via email or some other method to let Salesforce know that the transaction has gone through so that the payment can be closed. Can this be done?
Thanks for your help,
What do you mean by "so that the payment can be closed"? Are you just authorizing the transaction up front and then later capturing it when the products ship? Regardless, you can turn on relay response in SIM and then have the relay response page generate the email for you - or use a silent post page to do the same thing, whichever you prefer.
We've implemented SIM checkout in PaymentConnect for Salesforce (avail on the appexchange). This redirects the customer to SIM for the payment step during checkout and the posts back to a visualforce handler in Sites so we can mark a payment record in Salesforce "completed" and kick off any custom workflow required.
It can be done.