Recently I was facing an issue with one of the customers, whenever any user is trying to login into any environment the login screen redirects to another domain than the customer's domain.
After doing a bit of research and connects, I figured out that while deploying this tier-1 environment I have used my email id (which was not part of the customer domain). And system took my domain as the default tenant and ignored which azure connector was used to deploy this environemnt.
Solution: You have to use the customer's domain email to deploy any environment on their LCS so it will take their domain as default tenant than your(Partner/Vendor) tenant.
Now, this issue becomes more critical in case you rolled out a tier-2 or UAT instance (I haven't tied this but technically this can also happen), and non of the users can log in to this and you will end up, redeploying this from scratch. Imagine the scenario where your team already did the configuration on any of these servers and you end up redeploying, A complete mess. and a lot of rework.
However DB backup and DIXF export can cover you there, but again a lot of rework and time is needed. Plus justify this to your customer.
So, always use the customer's domain email id to deploy any environment for your customer.
If this issue might have been raised a few months back, I could have used the AdminUser provisioning tool (How to set new admin user) to change it, but with the recent update, this tool is deprecated. (Yeah I also didn't like this idea).
Hope this will help and save you from ending up in a similar mess.
Follow us on Facebook to keep in rhythm with us. https:fb.com/theaxapta