There are instances when the domain SPF, DMARC, and DKIM records are verified globally but a few emails that go out from the platform still land in the spam folder rather than the inbox.
In cases like this, to troubleshoot further, we may ask for a screenshot of the email received in spam as well as the email headers.
You can refer to this link below to get the email headers pertaining to which email services the partner/SMB is using. The email headers will help the email team troubleshoot further on the issue.
https://mxtoolbox.com/public/content/emailheaders/
https://www.ionos.com/help/email/general-topics/what-are-email-headers-and-how-can-i-view-them/
NOTE: Partner can save the email headers in a notepad/word file and share the same by email to the support team.