You might think that adding an email address to a security group would be an easy thing, but it seems to me that Microsoft has done everything in its power to make what was a simple task in Exchange 2003 a difficult one in an Exchange 2007 environment.
To be honest the process is really simple IF you are aware of one key factor. In order to mail enable a security group, you must first upgrade the group to a UNIVERSAL group. This part eluded me until I discovered the proper PowerShell code to add the mailbox attributes. At that point PowerShell tossed out a useful error message for me letting me know that the group type was incorrect.
OK, so now that we are armed with that knowledge, we find that adding mail attributes becomes a very simple task with PowerShell. You need only change the part of the command in red.
Creating A Mail Enabled Security Group 1. Make the group Universal 2. Open the Exchange Powershell Console 3. Execute the command: Enable-DistributionGroup -Identity "GroupNameGoesHere"
Note: you can specify the domain controller to use as well: Enable-DistributionGroup -Identity "GroupNameGoesHere" -DomainController dcname.company.com
4. Press Enter
If you prefer to use the GUI, once you have made your group a UNIVERSAL group, the group will then show up in the list of available groups when you select the New Distribution Group, From Existing Group options within Exchange Management console.
Whichever method you opted for, at this point the group has an email address matching the group name. You can add another address or modify the default one in Exchange Management Console. Expand Recipient Configuration, Distribution Group. Right click the group name in the right hand pane. Choose properties. Click the Email Addresses tab. Click Add to add a new address or Edit to alter the existing one. To set the default address, you must first remove the check in the box "Automatically update email addresses based on address policy". You can then select the desired address and click Set as Reply.