Creating / Changing a Delivery Routing Definition

Document created by user.oxriBaJeN4 Employee on Sep 12, 2015Last modified by user.oxriBaJeN4 Employee on Mar 27, 2017
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When an email is accepted by Mimecast for delivery, it is assigned to a Delivery Route Definition through a Delivery Route Policy and queued for Delivery. If the route information is no longer valid, it is possible to change the Delivery Route for that message by either:

  • Adjusting the Delivery Route Definition, taking care not to change the Description field.
  • Removing the original Policy that applied to the email, and applying a new Policy with an associated definition. The Recalculate button in the Delivery Queue forces Mimecast to review the current Policy that would apply to the email awaiting delivery. This feature is only available to customers utilizing our latest Gateway.


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 Delivery Routing Definition

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

    Give the definition a description.

    It is important this is not changed once it has been applied to a Delivery Routing Policy. Mimecast uses the route name to assign messages to the route. If the address for one of the routes changes, you can update the information, but don't modify the description. Renaming a route that is in use will result in delivery issues for any messages currently tied to that route.
    HostnameEnter a Public IP address or a publically resolvable DNS name. This IP address / hostname needs to be accessible from the internet for Mimecast to be able to use it as Delivery Route.
    PortSpecify a port number. The default value is TCP 25 (SMTP), unless there are other specific requirements.

    If your mail server is down for planned or unplanned reasons, Mimecast will continue to accept inbound email. The mail will be held in the Delivery Queue and Mimecast will attempt to deliver to the mail server based on the email delivery schedule. Once your mail server is back online, you can wait for the email to be delivered according to the schedule, or you can manually retry the messages held in your Delivery Queue. Mimecast will attempt to deliver email for up to 30 attempts over a period of 6320 minutes (4 days). If the outage is longer than this, Mimecast will issue a Non Delivery Report (NDR) to the email sender.


    If you are expecting to have an outage for longer than 4 days, it is possible to pause inbound mail delivery for an indefinite period of time. This can be done in using this option or via the Administration | Account | Settings menu item.

    Start DateIf the Pause option is selected, specify a date you want the delivery of inbound emails to be paused.
    Expiry DateIf the Pause option is selected, specify a date you want the delivery of inbound emails to stop being paused. You can use the Set to Eternal button to set the date to eternity. You can also use the Expire Now button to end the pause of inbound email immediately.
  6. Complete the Alternate Routes section as follows:
    Alternate Route

    Mimecast will always attempt to deliver emails to the primary route as specified in the Hostname field. In the event that the primary route is unavailable, alternate routes can also be specified. Mimecast will try the alternative routes in the order specified. Use the drop-down menu to select other Delivery Route definitions that have been saved.

  7. Complete the Optional SMTP Authentication Settings as follows:
    It is recommended that organizations select the mechanism that their email server supports natively as the first to be used. If they select an authentication mechanism is not successful, the next in the list will be attempted.
    Enable SMTP AuthenticationSome organizations require SMTP authentication before Mimecast is allowed to deliver email to their servers, which helps to increase the security measures for safe email delivery. The following authentication mechanisms are supported:
    NTLMThe standard used by Microsoft Exchange.
    Digest_Md5Uses RSA Data Security Inc.'s MD5 Message Digest algorithm
    Cram_Md5The CRAM-MD5 authentication method has been superseded by the DIGEST-MD5 method in terms of security. It is still provided here for compatibility with older SMTP servers that may not support the newer DIGEST-MD5 algorithm.
    PlainThe user name and password are sent unencrypted as per RFC 4616 stand. The username (for authorization), User Name (for authentication) and password. The three strings are grouped in a single string and base64 encoded.
    LoginIn the LOGIN authentication like in the PLAIN authentication, the username and password unencrypted but encoded in Base64. In contrast to the PLAIN authentication the two strings are transmitted in two steps.
    Authentication MechanismsThe available mechanisms are listed on the left, with the selected mechanisms on the right. Select a mechanism from a list and use the Add or Remove button to add it to the required list. Multiple mechanisms can be enabled. They will be utilized in the order listed in the Selected list. Select a mechanism from a list and use the Up or Down button to change their order of preference.
    UsernameSpecify the domain's username.
    PasswordSpecify the domain's password.
    DomainSpecify the domain.
  8. Click Save and Exit. The definition is ready to be added to a Delivery Routing policy.

Testing SMTP Delivery Routes

Mimecast provides the ability to test connectivity to your mail server.  This allows the Administrator to ensure that messages can be successfully delivered to the configured Delivery Route. Once the route details have been entered, click the Test Connection button in the top toolbar.


Monitor inbound emails using the Delivery Queue to ensure that the delivery is successful once a Policy has been implemented for the Delivery Route.  Once emails have been delivered, the Delivery Route used to deliver a specific message can be checked within Accepted Email or Archive Search results, within the receipt/delivery view.

Removing a Delivery Route Definition

To remove an existing Delivery Route, right click one of the routes from the list, and select Remove Route.  An error is displayed when trying to remove a Route that is referenced within a Policy. Additionally, it is not possible to remove a Delivery Route definition if an email has been processed by Mimecast but has not yet been archived, for example, a Held email, Accepted Email or delayed email. The definition is considered to be in use until all emails that the Delivery Route Policy has applied to have been delivered.  If an attempt is made to remove the Delivery Route definition, the following error is displayed:


"Unable to Delete - Definition is still in use by non-archived items. Please consider disabling the Policy for now so that you can delete it at a later stage."


Once these related emails have been archived, it will be possible to remove the Delivery Route definition.