Preparing to Rewrite Addresses in Multiple Domains
Microsoft Exchange Server 2007 will reach end of support on April 11, 2017. To stay supported, you will need to upgrade. For more information, see Resources to help you upgrade your Office 2007 servers and clients.
Applies to: Exchange Server 2007, Exchange Server 2007 SP1, Exchange Server 2007 SP2, Exchange Server 2007 SP3
Before you create an address rewrite entry that rewrites multiple domains, you must prepare your sub-domains. Also, before you perform any of the procedures that are described in How to Rewrite All E-Mail Messages from Sub-Domains, you must understand the requirements for rewriting e-mail addresses in multiple domains to a single domain, and the appropriate pre-configuration for the affected mailboxes and contacts.
Important Considerations
When you flatten internal sub-domains into a single external domain, you must consider the following factors, which apply only when multiple sub-domains are being rewritten:
Unique aliases are required All e-mail aliases, the part of the e-mail address to the left of the @ symbol, must be unique across all sub-domains. For example, if there is a joe@sales.contoso.com, there cannot be a joe@marketing.contoso.com.
Proxy addresses are required A proxy address that matches the e-mail address that is produced by the Address Rewriting agent must be configured on every e-mail account that is in the sub-domains that are rewritten. For example, if joe@sales.contoso.com is rewritten to joe@contoso.com, the e-mail address joe@contoso.com must be added as a proxy address to Joe's mailbox.
Contacts may be required If you are rewriting e-mail from a non-Exchange Server 2007 e-mail system, you must create Active Directory mail-enabled contacts for each e-mail address in the non-Exchange Server 2007 e-mail address that is being rewritten. This mail-enabled contact must contain the original e-mail address and the rewritten e-mail address. For example, if joe@unix.contoso.com is rewritten to joe@contoso.com, you must create a new mail-enabled contact in Active Directory with joe@unix.contoso.com as the target SMTP address and joe@contoso.com as the proxy SMTP Address.
These factors are important because rewriting addresses in multiple sub-domains causes a many-to-one relationship between internal sub-domains and the externally visible domain. Because of this many-to-one relationship, the Address Rewriting agent cannot determine which sub-domain contains the correct recipient when a message that is addressed to the externally visible domain is received.
Important
Make sure that every e-mail alias that exists across all sub-domains is unique. Exchange Server 2007 does not check to verify that every e-mail alias that can be rewritten to a single domain is unique.
Removing Conflicting E-Mail Addresses
To create an address rewrite entry that rewrites multiple sub-domains, you must first make sure that all e-mail aliases are unique across all your sub-domains. For example, consider the following configuration:
The following users are in the subdomains sales.contoso.com, marketing.contoso.com and research.contoso.com:
maria@sales.contoso.com
chris@sales.contoso.com
david@marketing.contoso.com
brian@marketing.contoso.com
chris@research.contoso.com
carter@research.contoso.com
Each sub-domain has two users, and each user has a unique e-mail address. However, you want to rewrite the subdomains sales.contoso.com, marketing.contoso.com, and research.contoso.com into a single domain that is called contoso.com. Table 1 shows each original e-mail address and its corresponding rewritten e-mail address.
Table 1 Original e-mail addresses and corresponding rewritten e-mail addresses
| Original e-mail address | Rewritten e-mail address |
|---|---|
maria@sales.contoso.com |
maria@contoso.com |
chris@sales.contoso.com |
chris@contoso.com |
david@marketing.contoso.com |
david@contoso.com |
brian@marketing.contoso.com |
brian@contoso.com |
chris@research.contoso.com |
chris@contoso.com |
carter@research.contoso.com |
carter@contoso.com |
When the e-mail addresses in each sub-domain are rewritten, a conflict occurs between chris@sales.contoso.com and chris@research.contoso.com, as indicated by the bold text in Table 1. Therefore, both e-mail addresses are rewritten to chris@contoso.com. To resolve this situation, you must change the e-mail address of one of the recipient mailboxes to an address that does not conflict with the e-mail address in any other sub-domain.
Applying Proxy Addresses to Recipient Mailboxes
For internal recipient mailboxes to receive replies to addresses that have been rewritten, you must configure those recipient mailboxes by using a proxy address that matches the rewritten external address.
For example, if a mailbox exists for carter@research.contoso.com, and the rewritten external address is carter@contoso.com, the mailbox must be configured by using a proxy address that is set to carter@contoso.com.