We have implemented several measures to address the issue with Google rejecting emails from our forums. Specifically, we've tightened our Sender Policy Framework (SPF), and added DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting, and Conformance (DMARC) protocols. It's noteworthy that DMARC compliance is not mandatory until February; therefore, our proactive approach puts us ahead in ensuring our email system's reliability and security.
These enhancements should hopefully resolve the Gmail delivery problems. If anyone is still having issues getting forum emails please let me know ASAP!