The placeholder domain structure increases security in the forest by segregating high-level schema-access accounts into a completely separate domain from the regular user domain. Access to the placeholder domain can be audited and restricted to maintain tighter control on the critical schema. The downside to this model, however, is the fact that the additional domain requires a separate set of domain controllers, which increases the infrastructure costs of the environment. Smaller organizations may have a difficult time justifying the extra infrastructure costs to provide the increased security, but whenever the budget allows, this model should definitely be considered.
@Post, It would be nice if the Exchange installation procedure was capable of removing a failed server in all circumstances. Regretfully, it is not - and this is a fact that has been pointed out to the development group by MVPs and others for many years. No improvement has happened, which is regrettable. We really need a switch in Setup that is something like /BlowAwayThisServerCosISaySo so that Setup would surgically remove all trace of an Exchange server from a Windows system. That request has been there for at least four years. In the meantime, if you get into trouble and the procedure to recover a failed server does not work, you really have no choice but to perform brain surgery with ADSIEdit. Sad, but that's life.
Yes, it's true that this leaves some trace of Exchange on a server, but at least you can then proceed to install Exchange on the box. I have done this many times on crashed servers.
Outlook’s Autodiscover will try several methods to retrieve the Exchange configuration information. After trying several HTTPS options Outlook will switch back to an HTTP option, so without the SSL security, and this gives a possibility to create a multi-namespace solution. An additional website is created on the Client Access Server, without the SSL implementation and this is a redirect website. The only downside of an additional website on your server is that an additional IP address is needed. For the default website of the IP address is used, for the redirect website () the IP address is used. An additional website is created in the Internet Information Server (IIS) Manager: