Hello Erol,
Thank you for posting in Microsoft Community.
I truly understand how you feel when it comes to DKIM support and personalize domains on Microsoft 365 subscriptions have been discontinued but is limited to new users, still there are existing ones. I indeed wanted to help, it just that we have limited resource and there is still no official announcement yet regarding when DKIM support will be enable for personalized domains.
What we can recommend is to really send a feedback directly to our development team. Please provide your experience as feedback to our developers. They'd love to hear from you about what's working well, what's not, and any ideas for improvements, including possible new features and functions. Your contribution will help us improve the user experience for you and all users around the world.
How do I give feedback on Microsoft 365? - Microsoft Support
Hoping for you consideration and cooperation on this matter.
Regards,
Prince R
Microsoft Moderator