There are different types of users in your
organization, as well as different types of needs for messaging
delivery. To account for those differences, Exchange provides various
types of recipients. Each recipient type fills a specific need within
your messaging environment. In this section, we will first outline the
various recipient types and then describe their purpose.
1. Mailbox-Enabled Users (Mailbox)
A mailbox-enabled user has an account in Active
Directory and a mailbox on an Exchange server. A mailbox-enabled user
can send and receive email messages within the Exchange organization
and through the Internet. A mailbox-enabled user also has access to a
personal calendar, contact list, and other services provided by the
Exchange servers. In most organizations, all corporate users have
mailboxes, and therefore store all emails on the Exchange servers.
Users who have a mailbox can use various client
applications to access mailbox content or send emails. For example,
they can use Office Outlook, Outlook Web App, or Exchange ActiveSync to
access all mailbox content.
When you create a mailbox-enabled user, there are
multiple types of mailboxes that can be created. For example, you can
create a standard mailbox that is associated with a user and then used
by a company employee to send and receive emails; or you can create a
resource mailbox that can be used to represent a company's resources,
such as a conference room.
2. Mail-Enabled User
At first glance, it just looks like a few letters
are missing to have a mailbox-enabled user, but a mail-enabled user is
quite different. A mail-enabled user has a user account in Active
Directory and an external email address associated with the account. The mail-enabled user has no mailbox on an Exchange server inside your organization.
All mail-enabled users appear in the corporate
global address list and can be used as a delivery recipient by any user
inside your organization (assuming that there are no restrictions in
place to prevent delivery).
So why would a company not
create a mailbox for a user; why would they only associate an external
email address with their user accounts? Well, the answer is that
mail-enabled users are used to fill a specific need: the need to make
an external contact appear in the internal address list. Yes, but there is already an object that fills that need, the mail-enabled contact (more on that recipient type later in this section). Well, the caveat here is that the external contact
needs access to internal network resources, by using an Active
Directory user account. An example of this would be an onsite contract
employee who requires access to the network but needs to continue
receiving email through their existing email address. As a result, the
mail-enabled user appears in the global address list and other users
can easily locate and send email to the address, even though the user
does not have a mailbox in the Exchange organization. Note also that a
mail-enabled user cannot send or receive email by using the internal Exchange servers.
3. Mail-Enabled Contacts
Mail-enabled contacts are exactly that: contacts
for individuals that are external to your organization. A mail-enabled
contact is an individual who has neither a security principal in Active
Directory nor a mailbox on an internal Exchange server. Mail-enabled
contacts are visible in the global address list, but they receive all
email on an external messaging system. Any internal user can send an
email message to a contact simply by selecting the contact from an
address list.
So what is the real-world purpose of a mail-enabled
contact? Well, imagine a company that has a large number of suppliers
or customers, with whom many internal users regularly communicate. You
may want to make it very easy for your internal users to locate and
identify these external contacts; by adding these contacts to Active
Directory, you are making them available from a central location and
accessible to all internal users. This also provides you with a way to
include the suppliers in distribution groups that are used for mass
mailings.
In Table 1, you can find a matrix that shows the core differences between the recipient types.
Table 1. Mailbox-Enabled Users, Mail-Enabled Users, and Mail-Enabled Contacts
Recipient | Needs Access to Internal Resources? | Needs a Mailbox in Exchange? |
---|
Mailbox-enabled user | Yes | Yes |
Mail-enabled user | Yes | No |
Mail-enabled contact | No | No |
Contacts can be created in Active Directory without
an Exchange infrastructure in place, but in that case, they are
essentially useless.
4. Mail-Enabled Groups
A mail-enabled group is an Active Directory group
that has been tagged with all the appropriate exchange mail attributes,
including an email address. Once a group has been mail-enabled, any
internal or external user can send mail to the group (assuming that
there are no restrictions preventing message delivery to the group).
The membership of the group can then be modified to configure who
receives emails that are sent to the group.
An Active Directory forest that does not include any
Exchange organization already uses groups to manage access to resources
and permissions. With the integration of an Exchange organization into
Active Directory, the same groups (security groups) can be mail-enabled
or new groups (distribution groups) that will only be used as a distribution list can be created and then mail-enabled.
Active Directory contains two types of groups:
distribution and security groups. Some organizations may decide to only
mail-enable distribution groups to prevent the likelihood of mistakenly
adding users to a group and assigning them access to secured resources.
This decision point should be made early on in an Exchange deployment
to ensure consistent use of groups.
A mail-enabled group can contain any type of
Exchange recipients, including other mail-enabled groups. In Exchange
Server 2010, you can only mail-enable universal groups.
5. Mail-Enabled Public Folders
A public folder is an electronic version of a
bulletin board. Public folders can be used to store messages, contacts,
or calendars that must be accessed by multiple users in your
organization. Users can create public folders by using Microsoft
Outlook, and administrators can create public folders by using the
Exchange management tools.
A mail-enabled public folder is a public folder that
has been tagged with all the appropriate Exchange mail attributes.
Mail-enabled public folders have an email address and can receive email
from any internal or external user from your organization (assuming
that the appropriate permissions have been configured for the folder).
Mail-enabled public folders are
particularly useful if you need to have a "virtual" shared mailbox
between multiple users. For example, you may want to have multiple
individuals of the HR department review the job applications that are
sent to your company. You can mail-enable a public folder and provide
an email address of [email protected].
As a last step, you would then provide the necessary permissions to
individuals in the HR department to review the contents of the folder,
without having a large number of emails polluting their inboxes.