I'm in the process of building a new Exchange 2007 environment. As you probably know, the Default e-mail address policy is based on your Active Directory domain name. I need to add our external DNS name as an e-mail address. I've determined three ways to do this: 1. Edit the Default e-mail address policy that appends your Active Directory domain name and change it to our external DNS domain name. 2. Add the external DNS name to the Default e-mail address policy. Each user will effectively have two e-mail addresses. 3. Create a new e-mail address policy. Each user would also effectively have two e-mail addresses. What is the best practice? Is the internal Active Directory e-mail address even necessary? What are the advantages or disadvantages to each option?

Hi,Well, before adding EAP, you need to add external Domain in accepted domain.1. In this option, old users will have both email addresses and new users will be having only external domain email address because when you change EAP, it doesn't remove existing/old email addresses from the properties of users.2. In this option all users (old and new) will have both email addresses.3. This is similar to option 1 since users fall under two different EAP, only high priority EAP applies on those so your new EAP applies but not default.So you don't have much difference between these three options since you will have to make external domain address as a primary SMTP address. I would go for option 3 to create new EAP with high priority and leave default as it is...References:Managing E-Mail Address Policies in Exchange Server 2007http://www.msexchange.org/articles_tutorials/exchange-server-2007/management-administration/managing-email-address-policies.htmlAmit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com