Understanding Users and Contacts
In Active Directory, users are represented as objects that can be mailbox-enabled or mail-enabled. A mailbox-enabled
user account has an Exchange mailbox associated with it. Mailboxes are
private storage areas for sending and receiving mail. A user's display
name is the name Exchange presents in the global address list and in
the From text box of e-mail messages.
Another important identifier for mailbox-enabled user accounts is the Exchange
alias. The alias is the name that Exchange associates with the account
for mail addressing. When your mail client is configured to use
Microsoft Exchange
Server, you can type the alias or display name in the To, Cc, or Bcc
text boxes of an e-mail message and have Exchange Server resolve the
alias or name to the actual e-mail address.
Although you'll likely configure most Windows user accounts as mailbox-enabled, user accounts don't have to have mailboxes
associated with them. You can create user accounts without assigning a
mailbox. You can also create user accounts that are mail-enabled
rather than mailbox-enabled, which means that the account has an
off-site e-mail address associated with it but doesn't have an actual
mailbox. Mail-enabled users have Exchange
aliases and display names that Exchange Server can resolve to actual
e-mail addresses. Internal users can send a message to the mail-enabled
user account using the Exchange display name or alias, and the message
will be directed to the external address. Users outside the
organization can use the Exchange alias to send mail to the user.
It's not always easy to decide when to create a mailbox for a user.
To better understand the decision-making process, consider the
following scenario:
-
You've been notified that two new users, Elizabeth and Joe, will need access to the domain.
-
Elizabeth is a full-time employee who starts on Tuesday. She'll work
on-site and needs to be able to send and receive mail. People in the
company need to be able to send mail directly to her.
-
Joe, on the other hand, is a consultant who is coming in to help out
temporarily. His agency maintains his mailbox, and he doesn't want to
have to check mail in two places. However, people in the company need
to be able to contact him, and he wants to be sure that his external
address is available.
-
You create a mailbox-enabled user account for Elizabeth. Afterward,
you create a mail-enabled user account for Joe, ensuring that his
Exchange information refers to his external e-mail address.
Mail-enabled users are one of several types of custom recipients
that you can create in Exchange Server. Another type of custom
recipient is a mail-enabled
contact. You create a mail-enable contact by specifying the external
e-mail address that users can use to send e-mail to that contact.
The Exchange Management Shell provides many commands for working with mailbox-enabled users, mail-enabled users, and contacts. The main commands you'll use are shown in the following list:
Understanding the Basics of E-Mail Routing
Exchange uses e-mail addresses to route messages to mail servers
inside and outside the organization. When routing messages internally,
Hub Transport servers use mail connectors to route messages to other Exchange servers, as well as to other types of mail servers that your company might use. Two standard types of connectors are used:
-
Send connectors
-
Receive connectors
Send and Receive connectors use Simple Mail Transfer Protocol (SMTP)
as the default transport and provide a direct connection among Hub
Transport servers in an organization. Hub Transport and Edge Transport
servers can also receive mail from and send mail to other types of mail
servers.
You can use these connectors to connect Hub Transport servers in an
organization. When routing messages outside the company, Hub Transport
and Edge Transport servers use mail gateways to transfer messages. The default gateway is SMTP.
Exchange Server 2010 uses directory-based recipient
resolution for all messages that are sent from and received by users
throughout the organization. The Exchange component responsible for recipient resolution is the Categorizer.
The Categorizer must be able to associate every recipient in every
message with a corresponding recipient object in Active Directory.
All senders and recipients must have a primary SMTP address. If the
Categorizer discovers a recipient that does not have a primary SMTP
address, it will determine what the primary SMTP address should be or
replace the non-SMTP address. Replacing a non-SMTP address involves
encapsulating the address in a primary SMTP address that will be used
while transporting the message.
Note
Non-SMTP e-mail address formats include fax, X.400, and messages originating from Lotus Notes. The Categorizer encapsulates e-mail addresses using non-SMTP formats in the Internet Mail Connector Encapsulated Addressing (IMCEA) format. For example, the Categorizer encapsulates the fax address, FAX:888-555-1212, as [email protected]. Any e-mail address that is longer than what SMTP allows is transmitted as an extended property in the XExch50 field.
In addition to primary SMTP e-mail addresses, you can configure alternative recipients
and forwarding addresses for users and public folders. If there is an
alternative recipient or forwarding address, redirection is required
during categorization. You specify the addresses to which messages will
be redirected in Active Directory, and redirection history is
maintained with each message.
