About Address Rewriting

By rewriting addresses you can ensure that the Email Appliance processes messages using the addresses associated with the appliance’s policy, while displaying the rewritten addresses to users. Address rewriting is particularly useful in cases when some or all of your email users are making the transition to a new address, or if you want any addresses that mail users see to be different from the addresses specified in the appliance policy.

Address rewriting should not be confused with alias maps, which are also supported on the Email Appliance. An alias map is a method for substituting an email address with another for the purpose of policy filtering, quarantine summaries, and user block lists (for more information, see “Enabling/Disabling Alias Maps”). Address rewriting, on the other hand, alters the address (and, optionally, the message headers) of an email message either before or after it is processed by the policy.

Regardless of your reason for rewriting addresses (examples are given below), you must provide valid entries for the Original address and Rewritten address. You can enter a complete email address, or just the domain portion of an address. All entries must include the “@” symbol. So, for instance, the following entries are valid:

  • user1@example.com
  • @example.com

These entries, however, are invalid:

  • user1
  • example.com

There are two rewrite types: “Recipient” and “Sender”. In some instances you may want to create corresponding recipient and sender entries. Recipient and Sender addresses are configured on separate tabs (as shown in the image below). When configuring addresses, it is assumed that "recipients" are destination addresses within your organization, and "senders" represent email accounts that are sending messages from within your organization.

There are a variety of reasons for rewriting email addresses. Here are some of the more common reasons:

  • Alternative/Vanity Addresses: If the corporate standard for email addresses is FirstName.LastName@example.com, you can use address rewriting to specify that the format of an address displayed in email messages is different from the one that the Email Appliance uses to process mail. For example, you can abbreviate John.Doe@example.com to JD@example.com :

    Rewrite Type Original address Rewritten address
    Recipient JD@example.com John.Doe@example.com
    Sender John.Doe@example.com JD@example.com
  • Replace Multiple Addresses with a Single Address: A member of your organization may have multiple email identities (for example, admin@example.com, webmaster@example.com, IT@example.com); however, for the purpose of processing mail, it often makes sense to rewrite these various recipient addresses to one address (John.Doe@example.com), so that mail for all these addresses are directed to a single account. To configure this particular example, you would create three separate entries on the Recipient tab.

    Rewrite Type Original address Rewritten address
    Recipient admin@example.com John.Doe@example.com
    Recipient webmaster@example.com John.Doe@example.com
    Recipient IT@example.com John.Doe@example.com
  • Replace Subsidiaries with Parent Company: Although a company may have one or many subsidiaries, it can create a consistent customer experience by making it seem as if all the email comes from a particular domain. So, if Company B (a subsidiary) provides support for Company A (a parent), you could rewrite the addresses so that customers direct their queries and comments to support@CompanyA.com, and they receive responses from the same address. In this case, messages addressed to support@CompanyA.com are rewritten by an Email Appliance at CompanyA and routed to support@CompanyB.com. Conversely, messages sent from staff using support@CompanyB.com are routed through the same appliance at CompanyA, rewritten to support@CompanyA.com, and sent back to the customer.

    Rewrite Type Original address Rewritten address
    Recipient support@CompanyA.com support@CompanyB.com
    Sender support@CompanyB.com support@CompanyA.com
  • Domain Changes: If your organization undergoes a merger, acquisition, or name change, there will likely be a transition period during which you want to continue accepting mail that is sent to old addresses while you are beginning to use the new addresses. Rewriting recipient and sender addresses allows you continue to honor the old addresses, even though those within the organization appear to be sending and receiving mail with the new addresses. For example, to rewrite addresses for everyone within a single domain who have been assigned to a new domain:

    Rewrite Type Original address Rewritten address
    Recipient @old.domain.com @new.domain.com
    Sender @old.domain.com @new.domain.com