If the buyer's order appears in your E-junkie Transaction Log, that confirms we processed their order and should have sent them any thank-you emails you have configured. I examined your settings and confirmed your product is properly set to send a thank-you email after payment or whenever you send a free link, and I issued myself a free test link to confirm that actually worked.
Most likely the affected buyer's email provider has a considerable delay in delivery or some other sort of filtering that deleted or blocked the message even before their spam folder filtering could see it -- e.g., they may have an aggressive email filter that blocks messages from any unrecognized address not already in their contact list/address book, pre-approved whitelist, or that they haven't sent to previously. Sometimes such filters send an autoresponse asking unrecognized senders to click a link or reply to confirm their address and allow the message through, but such autoresponders may not get to you depending on which email header they pick to respond to from the original message.
