Okay, so we have DKIM, SPF, and DMARC set up. Emails from the Salesforce system were sending through just fine until recently. Now, I just get relay messages marking the mail as undeliverable. I have gone through my DNS settings by myself and with two other professionals and still cannot get the mail to come through. This issue started after I created a sandbox org and subsequently deleted it. When I use the "Test Deliverability" feature, absolutely nothing will come through until 1-2 days later, which results in another undeliverable relay message. I need to be able to email reports to my team. How can I fix this? Any input would be greatly appreciated as there is little regarding this issue online.

Thank you!