Dynamic Distribution groups are Distribution groups that dynamically add members into the group based on a certain set of filters and conditions, when an email is sent to the group. These are great for mass mailing a group of users that change can often and managing the group manually would be difficult to maintain.

Exchange offers 2 ways of creating these groups; you can use the EMC/ EAC or PowerShell. I have found that the majority of cases for Dynamic Distribution can be created using the EMC/EAC, which offers the following set of pre-canned filters and conditional.

• IncludedRecipients
• ConditionalCompany
• ConditionalDepartment
• ConditionalStateOrProvince
• ConditionalCustomAttribute( 1–15)

There are times that this pre-canned list just doesn’t fit the bill. Let’s say you need a Dynamic Group that filters on users from a certain country or even a particular job title?  PowerShell to the rescue!

PowerShell offers the pre-canned filters as well as any of the account attributes that a user account would have, giving you a lot more freedom to create some customized Dynamic Distribution Group. Please note that you cannot combine pre-canned conditional filters and custom Recipient Filters in the same query.

For example, to create a Dynamic group for mailbox users only in a particular country and company, let’s say the US, use the following cmdlet:

New-DynamicDistributionGroup -Name "TestGroup" -Alias "TestGroup" -OrganizationalUnit "your/OU"-RecipientFilter {(RecipientType –eq  “UserMailbox”) -and (CountryOrRegion –eq “United States”) -and (Company –eq “mycompany”)}

If you have an existing group that you just need to modify to become custom use the Set-DynamicDistributionGroup cmdlet:

Set-DynamicDistributionGroup -Identity "TestGroup" -RecipientFilter {(RecipientType –eq  “UserMailbox”) -and (CountryOrRegion –eq “United States”) -and (Company –eq “mycompany”)}

Note that when creating your Dynamic Distribution Group using PowerShell you cannot combine pre-canned conditional filters and custom Recipient Filters. A list of all the available filterable properties  parameters can be found on TechNet’s site.

http://technet.microsoft.com/en-us/library/bb738157(v=exchg.150).aspx