@Hasham - First, I am happy to hear you were able to get these issues resolved with the custom build upgrade. With that being said, I don't believe there were any SPF/DMARC/DKIM related fixes in this build, so perhaps you had a temporary or intermittent issue happening here?

Next, because EAS/EWS/MAPI is not a 1:1 copy of Exchange, some parts of the Exchange Connectivity Analyzer tests will fail as we don't implement all of the same methods. This would explain why you are not having sync issues, but are still failing the connectivity tests. This is normal and expected, and you should have nothing to worry about. I hope this helps! :-)