Connect Application: Setting Up Your Outbound Email

Document created by user.oxriBaJeN4 Employee on Oct 22, 2015Last modified by user.oxriBaJeN4 Employee on Oct 10, 2018
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Routing your organization's mail starts with the outbound email for your validated internal domains. This allows us to build a list of your trusted senders, by monitoring who you send email to over several days.


Before setting up your outbound email, the following prerequisite steps should be completed:

  1. Validating Your Domains (compulsory).
  2. Setting Up Your Inbound Email (recommended).
    Depending on your Exchange type, visit the "Preparing for Inbound Email" page for either On Premise / Hybrid or Office 365 / Hosted Exchange / G Suite for further information.

Applies To...


  • New clients connecting with Mimecast using the Connect Application. If you're not using the Connect Application, click here.
  • Administrators with account permissions to configure a mail flow connector in the relevant Exchange type.




To set up your outbound email:

  1. Log on to the Connect Application.
  2. Click on the Platform | Set Up Your Outbound Email menu item.
  3. Click on the Start button.
  4. Confirm Your Outbound IP Addresses (applies to On Premise / Hybrid Exchange only).
  5. Update the SPF Records for your domain. This is an external task. 
  6. Validate your SPF Record in the Connect Application. This is a recommended optional step.
  7. Create an Outbound Email Flow Connector to route your outbound mail through us. Follow the instructions below according to your Exchange type. This is an external task.


Confirming Your Outbound IP Addresses


For an On Premise / Hybrid Exchange, you must confirm your outbound IP addresses. This ensures we only deliver legitimate email from your organization:

  1. Check that the Outbound IP Ranges displayed in the application are correct.
  2. Click on the Confirm button to continue.
If the outbound IP addresses are incorrect, click on the Notify Us link in the information box. This displays the "Contact Support" dialog where you can let our implementation team know of any changes.

Updating Your SPF Records


To specify Mimecast as the authorized outbound mail service:

  1. Update the SPF records for your domains with the information displayed in the Connect application:
    SPF Record Entry
    Only use the SPF record displayed in the application for your domains, as there are regional differences (i.e. "eu" for Europe in the above example). If you're not the person responsible for this task, click the Share link to send an email containing the required detail to someone who is.
  2. Log on to your Domain Registrar.
  3. Update / replace each domain’s SPF record to specify us as the authorized outbound service.
  4. If all email for your domains will be routed via us, remove all previous SPF records.
  5. Other outbound sources for your domain may require a combined SPF record. In this instance, ensure you include the Mimecast "" entry before creating a mail flow connector. To determine what "xx" is, refer to step 1 above.
    See the "Implementing SPF for Outbound Email Delivery" section in the Configuring DNS Authentication policies page and the Implementing SPF for Outbound Email Delivery page for additional information.

Testing your SPF Records


To test your SPF record:

  1. Navigate to Platform | Set Up Your Outbound Email in the Connect Application.
  2. Select your domain from the Record to Validate drop down menu.
  3. Click on the Validate button. One of the following messages will display:
    • A green tick confirms the SPF record is valid.
    • A red exclamation confirms the SPF record is invalid.
  4. Click on the More or Less links to view further information about the SPF record and toggle the display.
This step performs a TXT record lookup and validates the SPF record entry. You can have more than one mechanism (IP/Host), but Mimecast must be the first one listed.

Creating an Outbound Email Flow Connector


To create an Outbound Email Flow Connector, follow the instructions below according to your Exchange type. Once these external tasks are configured, click the Confirm button in the Connect Application to verify the connector. If validation is successful, a summary page displays of your outbound email flow. 


Office 365 / Hosted Exchange


  1. Log on to the Office 365 Exchange Management Portal.
  2. Create a mail flow connector. Read the Creating an Outbound Email Flow Connector page for further details.
  3. Ensure that all outbound emails are routed via the Mimecast Outbound Smart Hosts listed in Connect.


On Premise / Hybrid Exchange


  1. Log on to your Exchange Management Console.
  2. Create a mail flow connector. Read the Creating an Outbound Email Flow Connector page for further details.
  3. Ensure that all outbound emails are routed via the Mimecast Outbound Smart Hosts listed in the application.


G Suite


To prepare your outbound G Suite hostname, follow these steps:

  1. Create a mail route that uses the Mimecast Outbound Smart Hosts listed in Connect. 
  2. Create a mail route that uses the Google Internal Sending Hosts listed in Connect. 
  3. Configure two mail routing rules that:
    1. Use our smart hosts to send outbound mail.
    2. Use the Google internal sending hosts to send internal mail.

To create mail routes:

  1. Log on to the Google Admin Console.
  2. Navigate to Apps | G Suite | Gmail | Advanced Settings.
  3. Click on the Hosts button.
  4. Click on the Add Route button.
  5. Enter a Route Name (e.g. Mimecast Outbound Host).
  6. Select Multiple Host and enter the Mimecast Outbound Hostnames for your Mimecast region. Both must be marked as primary. See the "Outbound Send Connectors section of the Mimecast Gateway page for full details.
  7. Click on the Save button.
  8. Click on the Add Route button.
  9. Enter a Route Name (e.g. Internal Sending Host).
  10. Select Multiple Host and enter the Google Apps MX Records (ASPMX.L.GOOGLE.COM. and ALT1.ASPMX.L.GOOGLE.COM).
  11. Click on the Save button.

View the Add Mail Routes for Gmail Delivery page in the Google support site for further information.

To configure routing rules:

  1. Click on the General Settings tab.
  2. Navigate to the Routing section.
  3. Click on the Configure button.
  4. Select the Outbound option in the "Messages to Affect" section.
  5. Select the Change Route option in the Route section.
  6. Select the Route Name created in step 5 of the "Preparing Your Outbound Hostname" section.
  7. Click on the Add Setting button.
  8. Click on the Add Another button.
  9. Select the Internal | Sending option in the "Messages to Affect" section.
  10. Select the Change Route option in the Route section.
  11. Select the Route Name created in step 9 of the "Preparing Your Outbound Hostname" section.
  12. Click on the Add Setting button.

View the Set up an outbound mail gateway page in the Google support site for further information.

See Also...