Vendors and Customers are reporting that our email communications to them with invoices and sales orders or even support cases are sometimes being placed in quarantine. While doing some digging we found out NetSuite uses SparkPost for email delivery and some IP addresses associated with their SparkPost setup are black listed for potential spam. We contacted NetSuite and they cannot possibly monitor all email services that provide quarantine black lists. We need to contact the IT department of every single vendor and customer we email to notify them of the problem and ask them to white list these addresses in their email service. Has anyone else experienced problems with NetSuite emails being sent to spam or with NetSuite not wanting to support their service?

Yes, it's a standard problem, even with proper DKIM etc. Utter pain