Hello,
Thank you for your question. Have you tried following the doc [1] while trying to set up the MX records? This GCP doc will provide you a step by step guideline on how to perform this.
Also, It is worth mentioning that Google Groups is a place for non-technical how-to questions (where you're likely to find information like service status updates and release notes, and ranging from book recommendations to creative shortcuts) [2].
Therefore, I would recommend you to consider reaching out to Stack Exchange sites [3] (e.g. Server Fault )where Google also participates that can help you find answers and troubleshoot problems.
If you find any indication of a GCP specific issue, you may consider reporting [4] the issue with Issue Tracker with all the details [5] (omitting PII/sensitive information). You may also file a case with the GCP Support [6] and we will be more than happy to help.
Regards
Anik
Reference:
[2] Discussions: Google Groups: https://cloud.google.com/support/docs/community#discussions_google_groups
[3] Ask Technical Questions on Stack Exchange Sites: https://cloud.google.com/support/docs/stackexchange
[4] Create new issue: https://cloud.google.com/support/docs/issue-trackers#trackers-list
[5] Report Issues with Issue Trackers: https://cloud.google.com/support/docs/issue-trackers
[6] GCP Support: https://cloud.google.com/support-hub