Office 365 and Mimecast Archiving

Mimecast Enterprise Vault is an Archiving platform. They are an Offsite Archiving solution should you want your emails Archived. We in South Africa, have to be concerned about international bandwidth. What happens when we cannot connect? The Mimecast Archiving Solutions works as the MX records will point to the solution and then gets relayed back to Office 365. They will capture the emails inbound and outbound and archive it. Should there be mail issues, you now have to chat to multiple vendors. The other option is journal the emails to their solution, so they may Archive it.

Therefore, the MX records will point to Office 365 and outbound delivery will go straight out from Office 365. You can create a journal rule from Office 365 to Mimecast. Here is pre-setup which needs to be done on Mimecast side before configuring on Office365:

  • Create a Journal Definition In Mimecast
  • Configure Journaling Sub Domain in Mimecast
  • Contact Mimecast to add customer’s domain under the O365 umbrella

Then we move onto configuring the Office 365 side.

Configure an External Contact in Office 365

  • Log onto the Office 365 Portal. Select the “Exchange Admin Center” > “Recipients” > “Contacts”

  • Click on the + Icon to create a new contact. Ensure that the External Email Address is the same which is used in the Mimecast Journal Connection and which you created on the Mimecast Portal

Configure the Office 365 Send Connector to Mimecast

  • On the Exchange Admin Center, Select “Mail Flow” > “Connectors

  • Click on the + icon to create a Send Connector. These are the configs you need to enter:

From: Office 365

To: Partner Organization

Name of the Connector: Example Office 365 to Mimecast

Description: Explain what the connector does

Turn it on: Yes

  • Ensure the Only when email messages are sent to these domains option is selected

  • Click the + Icon and Add the domain in the dialog box which will appear. This should be the journal domain which was created on the Mimecast Portal.

  • Click “OK” and then select “Route emails through these smart hosts

  • Mimecast has a variety of Smart Hosts address which can be used based on the country you are in:
Region Hostname
North America

Europe and Australia

South Africa


Off Shore

  • Click on “Save”. The next steps with be security when communicating with the Smart Host. Leave by default which should have the “Always use TLS” enabled with “Issued by a trusted CA

  • Click “Next”, then click on the + button to add the email address. Add the email address and validate. Then click “Save”.

Create the Office 365 Journal Rule

  • On the Exchange Admin Center, select “Compliance Management” > “Journal Rules

  • Click on the + button to add a New Journal Rule. Here are the details to add:
Field Description
*Send Journal Reports Enter the email address of your journal contact. This address will receive the journal reports.
Name Enter a name for the journal rule.
*If the Message is Sent to or Received From Select the “Apply to all Messages” option form the drop down.
*Journal the Following Messages Select the “All Messages” option form the drop down.
  • Enter a service mailbox to receive a Undeliverable Journal Reports. Click “Save”.

Once done, the rule can take up to 24 hours for propagation time as it has to update all the servers Globally. Then you should be able to confirm on Mimecast Archiving Solutions Portal.

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