Reconfiguring third party security solution connectors to work with Exclaimer Cloud


When using Exclaimer Cloud with a third party security solution (for example: Mimecast; Proofpoint; Barracuda; Reflexion etc.), you may find that emails do not route the way you would like them to.

The recommended setup for Exclaimer Cloud in conjunction with a third party security solution is as follows:
Sender > Office 365 > Exclaimer Cloud > Office 365 > third party security solution > Recipient.


Note: This solution assumes that you have already configured the Exclaimer Cloud rule and connectors, if not please run the setup wizard from within the Exclaimer Cloud portal.

For example purposes, we are using Mimecast, however the same process applies for any third party security solution.

Currently, the Mimecast connector is set to apply to all messages at the connector level and commonly appears similar to the following connector:

Send to Mimecast.

When do you want to use this connector?

How do you want to route email messages?

The above setup shows the correct SMTP address for the Mimecast smart host, but this setup bypasses Office 365 Transport Rules.

The objective of this solution is to modify the connector setup so that it uses a Transport Rule with a lower priority than the Exclaimer Transport Rule, therefore ensuring that signatures are applied before messages are scanned by Mimecast.

Please follow the steps below to reconfigure the Mimecast connector (note that there may be downtime during the change - we recommend making this change out of hours where possible):

Step 1: Reconfigure the Mimecast connector

  1. Log on to the Office 365 Portal as a Global Administrator.
  2. Open the admin center.
  3. Click admin centers and select Exchange.
  4. Select mail flow and then connectors.
  5. Reconfigure the Mimecast connector to apply Only when I have a transport rule set up that redirects messages to this connector:

    Select transport rule radial option.
  6. Leave all other connector settings as they are and save the connector.

Step 2: Add a new mail flow rule

  1. Still in the admin center under mail flow, select rules.
  2. Click the + (plus) button to add a new rule.

     Create a new rule.

  3. Give the rule a name - for example: Send to Mimecast.

Step 3: Configure the new mail flow rule

  1. Scroll down and click the More options link to enable additional rule options.
  2. Add a condition which states The sender is located inside the organisation. This ensures that all emails sent from your Office 365 tenancy are routed through the connector.
  3. Add an action which states Redirect messages to the following connector and select your Mimecast connector. The rule should now resemble the example below:

    Redirect messages to the Mimecast connector.
  4. Save the new rule. It should now be shown in the rules list with a priority of 1. Also in this list, you should see an Exclaimer rule called Identify messages to send to Exclaimer Cloud, which has a priority of 0:

    Identify messages to send to Exclaimer Cloud.
  5. Open the rule named Identify messages to send to Exclaimer Cloud.
  6. Scroll down until you see the option to Stop processing more rules:

    Choose the stop processing more rules option.

  7. Select this option to force the Exclaimer rule to run and to prevent Office 365 from running the Mimecast rule until the email is returned from Exclaimer Cloud with a signature attached. At this point, the Exclaimer Transport Rule will have its exception triggered by the Exclaimer message header once it returns, and the Mimecast rule will be used instead.
  8. Your Office 365 set up is now complete and mail should start flowing as normal again.

Step 4: Add your .onmicrosoft address to the Exclaimer portal

The final step of this process is to return to the Exclaimer Cloud portal to ensure emails are routed to Office 365 once the signature has been applied:

  1. Log in to your Exclaimer portal.
  2. Select Launch for your subscription

  3. Select Settings in the Cloud portal

  4. Select Mail Flow.
  5. Under Mail Routing, select
  6. Select Static domain.
  7. Enter your .onmicrosoft address (listed in your Office 365 tenancy under Domain Name):

    Mail Routing options in Exclaimer Cloud - Signatures for Office 365.

  8. Save changes.

Your setup is now complete. When you send a test email, you will be able to see (from the message headers) that the email routes from Office 365 to Exclaimer Cloud, then from Exclaimer Cloud back to Office 365 and from Office 365 to Mimecast - as expected.

If you experience any problems, or if you would like to have someone from Exclaimer on the telephone or via a remote session during the setup process, please let us know or raise a support ticket here.

Haven't found a solution to your problem?

Please click the button below, login to the Exclaimer Cloud portal and raise a support ticket. A member of the Exclaimer Support team will then be in touch.

Raise a support ticket