Hello there, user29831.
QuickBooks uses the notification.intuit.com or quickbooks@notification.intuit.com our sender address. Some email domains may block @intuit.com communications on our servers. That’s why any email coming from us are moved to our junk or spam folder.
Within QuickBooks, we can check the Tasks section shown in our Dashboard to view errors when sending transactions. From there, we’ll be able to see our customer emails who had errors in receiving the transaction. To prevent this from happening again, we can add approved email addresses for your email provider.
I'm here if you need anything else. Thanks!