Emailed Receipts delivered to spam

Our RENXT receipts are ending up in spam for gmail every single time. We set up our SPF records and DKIM as recommended by Blackbaud. Email headers show SPF and DKIM pass, but DMARC fails. Gmail says they can't authenticate the sender, and this does not appear to be related to the content of the email. I assume that is because our From address does not match the actual sending server, which—based on the headers—would appear to be convio.net Anybody have any insights on how to keep our RENXT automated receipt emails out of Google's spam folder? Something to add to our SPF record? Changing the From address?