Authorize.net e-mail not sent to customer when cardholder name not complete

Hey gang,

Weird problem that I'm trying to eliminate causes.

Normal, typical operation:
* Donor completes the form ( https://utcatholic.org/support/donate/ ).
* GF produces notification sent internally to staff
* Authorize.net produces receipt that is sent to merchant (utcatholic) and to the donor.

This has worked fine for awhile now. The box is checked in settings for Authorize to send receipt.

However, if the donor does not include the "cardholder name" in the credit card area, the e-mail to the donor is NOT sent. GF produced notification and Authorize.net produces a receipt sent to the merchant.

Authorize's support was no help, basically blaming the various possible hiccups in sending e-mail, but I've tested it multiple times with different e-mail addresses on different providers.

Only thing I can think of now is something either with the GF Add-On or the Authorize API that silently balks at lack of cardholder name.

Thanks in advance!

Yes--the transaction is successful in every other way.

Edit: The email address is recorded with Authorize. I wonder if lack of cardholder name impacts the GF setting to trigger an Authorize.net rcpt.