@Arman Avetisyan Here are the steps you can follow:
- Sign up using an admin user in your company.onmicrosoft.com tenant: This will ensure that the Azure AD is shared between your Azure subscription and your Office 365 subscription. This is a standard practice.
- Check the Azure portal and Office 365 setup: You can verify this by checking the Azure portal section
Azure Active Directory > Custom domain names
AND in Office 365 >Admin > Setup > Domains
. You should see the same domains configured in both interfaces.
Two Azure Active Directories cannot have the same domain. Technically, an Office 365 instance with a tenant name (.onmicrosoft.com) is an Azure AD. Office 365 is just a SaaS application attached to every Azure AD. So, if you have a domain abc.com under a tenant - contoso.onmicrosoft.com (doesn’t matter whether it’s in Office 365), you can view this directory in the Azure Classic portal.
Please note that you should not delete the domain from your Azure services as it might disrupt your app server. Instead, you should try to integrate the domain with both Azure and Office 365.