Hello @Daryl Bajuelo
Based on your description, it appears that new Microsoft 365 groups are being created with the wrong domain because that domain is currently set as the default in your Microsoft 365 settings.
To resolve this, please go to the Microsoft 365 Admin Center, navigate to Settings > Domains, and set your preferred domain as the default. This will ensure that new groups are assigned the correct domain for their email addresses.
I hope this information is helpful. If you have any further questions or need additional assistance, please don’t hesitate to let us know — we’ll be happy to help.