imagine some employees are already using Azure resources like App Services, SQL databases and DevOps for our custom domain company1.com. All users that access these resources have email addresses and AD logins like firstname.lastname@example.org and so on.
Now we'd like to use Office 365 for all users in the company. Our consulting partner told us that we must free our company1.com domain to connect it with a new O365 tenant.
We should register a new AD tenant for our Azure resources with a new domain named company1.onmicrosoft.com.
We scare that in the furure we'll have to use two accounts - one for Azure and the other for O365.
So now my question is: Isn't it possible to use O365 along with other resources side-by-side in the same tenant domain company1.com?