Custom Domain as default

[AzSupport]

We have installed AD FS and synced all users from on-prem AD to Azure AD. We have added UPN for custom Domain in the AD and also verified the custom domain. We can see all on-prem ad users in the Azure AD as user@customdomian.com. and also SSO works.

But I do not have an option in the AD to create a user@customdomain.com instead I can only create a user@customdomian.onmicrsoft.com. I tried to join a device to Azure AD and it is only possible for me to join a device with user@customdomain.onmicrosoft.com, not with user@customdomain.com.

I was expecting the Azure AD should have an option for both default AD domain(customdomain.onmicrosoft.com) and customdomain (customdomian.com).

Can someone advise me, please?

[#2]

You need to create the users on onprem AD they will then get synced to Azure AD via connect. If you create users on Azure AD, they will remain on Azure AD only mastered by Azure AD.

To join a device to Azure AD you need to use the credentials of a global administrator.

[#3]

@AzSupport

Hi, so when in Azure, looking Azure Active Directory, what are you seeing under Azure AD Connect? Are you showing any issue?  Has Azure AD Connect been installed on-prem? If so, what issue does it show?