Creating / Changing an Address Alteration Definition

Document created by user.oxriBaJeN4 Employee on Sep 12, 2015Last modified by user.oxriBaJeN4 Employee on Jan 23, 2017
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Address Alteration definitions can be created in the root folder or in a subfolder. If entered into the root area, no policy is required. Anytime a match is found, Mimecast rewrites the address. If you only want certain addresses to be amended in certain traffic flows, the address alteration should be created in a subfolder. In this instance, an Address Alteration policy must be configured to specify when the address alteration should apply.


The destination server must be configured to accept emails with the altered address. Additionally if rewritten address emails are sent but cannot be delivered to the next hop mail server, the postmaster sends a the Non-Delivery Report (NDR) to the rewritten address (i.e. not the original address).


Address rewrites also support the concept of specificity. Within a single rewrite set, ‘one to one’ email addresses take preference over local part policies, which in turn take preference over domain level rewrites.




To create or change a definition you must:

  • Be logged on to the Mimecast Administration Console.
  • Have access to the relevant Gateway menu item for the definition being created or changed.


Creating / Changing a Single Address Alteration Definition


To create a single Address Alteration Definition:

  1. Open the Gateway Policy Editor.
  2. Select the Definitions drop down. A list of the definition types is displayed.
  3. Select the Address Alterations definition type from the list. The list of definitions is displayed.
  4. Either select the:
    • Policy to be changed.
    • New Address Alteration button to create a definition.
  5. Complete the Address Alteration Properties as follows:

    Original AddressEnter the original email address.
    New AddressEnter the new email address.
    Applied RouteSpecifies the route for inbound, outbound, or inbound and outbound messages.
    Address Type

    Specify what address type will be altered. The options are:

    Address TypeDescription
    Applies to All AddressesAll Header and Envelope addresses will be modified.
    Envelope FROM AddressOnly the main sender SMTP address will be modified.
    Envelope TO AddressOnly the main recipient SMTP address will be modified.
    >Header [From] Address>Only the main sender Header address will be modified.
    Header [Reply-To] AddressOnly the Reply To Header address will be modified. This can be used in circumstances where the address details should not be modified, unless the recipient chooses to reply to an email. In this instance the email can be sent to a different email address / domain.
    Header [To/Cc/Bcc] Address(es)The Header addresses contained in any of the To/CC/BCC fields will be modified.
  6. Select Save and Exit.

An asterisk (*) can be used in the "Original Address" and "New Address" fields to substitute email address information. For example, if the asterisk is present in the field prior to the @ symbol, and the domain name is entered after it, all the company's email addresses will be altered to the new address.

Creating Multiple Address Alteration Definitions


You can create a number of Address Alteration definitions in one go by entering their details using the following process. You may find it easier to have the data ready in another application (e.g. Microsoft Excel). Just create a file without a header row and with four columns. Once the file is ready, export it in a tab delimited format and paste the content into the text box in step 6. The Bulk Additions feature accepts simple spaces between columns and fixed width columns. However double quotes are not accepted.


To create multiple Address Alteration definitions:

  1. Open the Gateway Policy Editor.
  2. Select the Definitions drop down. A list of the definition types is displayed.
  3. Select the Address Alterations definition type from the list. The list of definitions is displayed.
  4. Select the Build button. A drop down is displayed.
  5. Select the Bulk Addition menu item. A text box is displayed.
  6. Add the detail of each definition on a separate line using the following format:

    FieldDescriptionValues AllowedValue Descriptions




    The "all" value allows you to specify both inbound and outbound traffic.
    2Address Type







    The "all" value allows you to create a rewrite entry that works on all addresses regardless of envelope or header.


    The [ ] brackets specifically indicates the envelope FROM, rather than the header FROM.


    No brackets indicate the header address.

    3Old Address




    4New Address




  7. Click Save and Exit to create the definitions.


For example:


See Also...