How to Configure Google Workspace Outbound Filtering Using Routing Rules

Last updated on 2025-02-07 12:32:30

In certain situations, customers using Barracuda Networks to filter outbound emails may find that specific types of messages are restricted from being relayed. This occurs because Google does not support SRS (Sender Rewrite), and Barracuda Networks does not allow relaying for unverified domains. To address this, Google Workspace can be configured to route outbound mail based on routing rules. These rules will allow emails to bypass outbound relay through Barracuda Networks and instead be sent directly to the Internet.

Note: If you were previously using the default outbound configuration for routing, you must remove that setup before establishing mail flow rule routing.

Add Outbound Smarthost

Log into https://admin.google.com/ac/apps/gmail/hosts.
Click Add Route.
Enter a route Name.
For Specify email server, select Single host, and enter the outbound hostname from Email Gateway Defense. Enter 25 for the port number.
Tip: Go to Email Gateway Defense, and click the Domains tab. Copy your outbound smarthost from the MX records.
Keep the following default options:
- Uncheck Perform MX lookup.
- Check the following:
  a. Require mail to be transmitted via a secure (TLS) connection (Recommended).
  b. Require CA signed certificate (Recommended).
  c. Validate certificate hostname (Recommended).
Click Test TLS connection to verify the connection to the receiving mail server.
Click Save.

Create Routing Rule

Note: The instructions below will focus on resolving issues related to users sharing Google Files with external contacts. Depending on the specific email types you need to bypass, you may need to include additional criteria to search for.

Log into https://admin.google.com/ac/apps/gmail/compliance.
Go to Content compliance and click Configure or Add Another Rule if an existing rule is already in place.
Enter a name/description.
For Email messages to affect, select Outbound.
Click Add to add a new expression.
In the pop-up window, select Advanced content match.
Select the following options:
1. Location – Select Sender header.
2. Match type – Select Not contains text.
3. Content – Enter google.com.
Click Save to save the settings.
In the main window, under If the above expressions match, do the following,
1. Under Route, select Change route.
2. From the drop-down list, select the route you created above in Add Outbound Smarthost.
Click Save.