New Domain Tree or Child Domain

Can anyone tell me the difference from a management stand point between creating a new domain tree in an existing forest or a child domain. What is the pros and cons of this? Thanks

If you want to manage multiple domain tree forest, then it is more complex than one with contiguous namespace, so the second one is the most recommended. You should actually conside using a single domain forest seriously, unless you have a good reason to split it into many domains.

Even I agree with the above post, if you really want to create another domain then create a child domain rather than going for a multi-domain tree. But in any case, why are you trying to create another domain, anyhow?

I have a very basic conceptual question. We have a software which is a virtual appliance running in the cloud. We provide each of this appliance to our customers. We are trying to hook this appliance to LDAP in Windows Server 2003 in such a way that different users at different customer companies can access our appliance securely.

I tried creating different OUs for each of the customers under a single domain say test.com. But, the problem here is that all the users are getting an email address say alice@test.com. I don't want this to happen. I want users from different companies to have their email addresses assigned based on the domain of their company. For example, if Alice is in CompanyA and Bob is in CompanyB, I want their email addresses to be Alice@companya.com and bob@companyb.com.

I am not able to achieve this if I create different OUs. Is it advisable for me to create different domains for different customer companies in this case? If yes, how do I go about it?

Any help would be greatly appreciated.