Blackbaud is capable of sending DMARC compliant email because they support custom DKIM configurations that achieve DMARC alignment. Blackbaud is an Outreach Platform and is often used by Marketing, Product or Application Development teams.
The links just below are resources on how to configure this source to send DKIM-aligned email on your behalf. You will complete this configuration by (1) following the source's instructions and (2) adding the required entries into your DNS. https://docs.blackbaud.com/email-resource-center/faqs/best-practices-faq#what-is-dkim-and-how-do-i-add-it and https://docs.blackbaud.com/email-resource-center/overview/client/sender-authentication/dkim
It appears that this vendor cannot send customer email with SPF alignment. As such, you should not have it listed in your SPF record.