Use the steps in this article if you have multiple domains within your Office 365 tenant and you want to scan only certain domains outbound.
Step 1. Create the Connector
- Log into the Office 365 admin center, and go to Admin centers > Exchange.
- In the left pane, click mail flow, and click connectors.
- Click the + symbol and use the wizard to create a new connector.
- From the From drop-down menu, select Office 365, and from the To drop-down menu, select Partner organization.
- Enter a Name and (optional) Description to identify the connector:
- Click Next. Select Only when I have a transport rule set up that redirects messages to this connector:
- Click Next. Select Route email through these smart host, and click on your outbound hostname:
- Click Next. Use the default setting, Always use Transport Layer Security (TLS) to secure the connection (recommended) > Issues by Trusted certificate authority (CA):
- Click Next. In the confirmation page, verify your settings and click Next. Office 365 runs a test to verify your settings:
- When the verification page displays, enter a test email address, and click Validate. Once the verification is complete, your mail flow settings are added.
Step 2. Create Transport Rule
- Log into the Office 365 admin center, and go to Admin centers > Exchange.
- In the left pane, click mail flow, and click rules.
- Click the + symbol, and click Create new rule.
- In the new rule page, enter a Name to represent the rule.
- Click more options towards the bottom of the page.
- From the Apply this rule drop-down menu, select The sender is located > is external/internal > Inside the organization.
- Click Add Condition.
- From the drop-down menu, select The sender's domain is....
- Enter the domains you want to route through the Barracuda Email Security Service.
- From the Do the following drop-down menu, select Redirect the message to… > the following connector, and select the connector you defined in Step 1. Create the Connector.
- Click Add Exception.
- From the drop-down menu, select The Recipient is located > is external/internal > Inside the organization.
- Towards the bottom, from the Match sender address in message drop-down menu, select Header or envelope.
- Click Save.