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How to Configure G Suite for Inbound and Outbound Mail

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This article addresses configuring G Suite Business and Education editions with the Barracuda Email Security Gateway as your inbound and/or outbound mail gateway.

Inbound Configuration

  1. Log into the G Suite Domain Management Portal.
  2. Navigate to the Settings tab and then select Email under the Services section.
  3. Navigate to Inbound Gateway and enter the public IP addresses of the Barracuda Spam Email Security Gateway(s), specifying either the block of addresses or individual IP addresses.

Figure 1: G Suite - Inbound Gateway Settings


Make sure to check the box:  Only let users receive email from the email gateways listed above. All other mail will be rejected.  More info on inbound gateways can be found here.

Outbound Configuration

  1. Navigate to the Settings tab and then select Email under the Services section.
  2. Navigate to Outbound Gateway and enter the IP address of the Barracuda Email Security Gateway that is the outbound mail gateway.

Figure 2: G Suite - Outbound Gateway Settings

4-28-2012 2-42-54 PM.png

More information about outbound gateways can be found here.

G Suite IP Addresses can change so please refer to this Google documentation.

Additional settings:

  • nslookup -q=TXT _netblocks.google.com
  • server: google-public-dns-a.google.com
  • address:
  • Non-authoritative answer:

_netblocks.google.com text ="v=spf1 ip4:

ip4: ?all"

Configuring the Barracuda Email Security Gateway

  1. Navigate to DOMAINS > Domain Manager and specify your domain in New Domain Name, then click Add Domain.
  2. Click the Manage Domain link and then BASIC > IP Configuration. Add the G Suite destination mail servers as follows:













Also add the Destination Server name/IP address or hostname that receives email after spam and virus scans. It is usually best to use a hostname rather than an IP address so that the destination mail server can be moved and DNS updated at any time without having to make changes to the Barracuda Email Security Gateway configuration.

If you set Use MX Records (on the same page) to Yes, you must enter a domain name for this field. If multiple servers are specified, then the delimiter used determines the behavior (see below). Note that you can either configure Use MX Records for all domains from the BASIC > IP Configuration page, or you can configure it per-domain from DOMAINS > Domain Manager > Manage Domains, then using the BASIC > IP Configuration page for the domain you choose to manage. It is NOT recommended to set Use MX Records to Yes to avoid a potential mail loop.

  1. Comma (",") or semi-colon (";") - Each entry in the list will used in round-robin fashion, with relative weights determined by the number of times a particular entry is listed.
  2. Space (" ") - Each entry in the list will be treated as a failover list, with an entry being used only if all entries preceding it in the list are unreachable.

For more information about what it means to use MX records, please see Using MX Records.

How to Configure G Suite to Bypass the Barracuda Email Security Gateway for Internal Mail 

In the G Suite Admin console:

  1. Click on Apps-> Gsuite-> Gmail-> Advanced Settings.
  2. Click on the Hosts tab. Under Edit mail route, add the host for internal email as shown below and save.
  3. Return to the Advanced Setting page and go to the General Settings Tab. Scroll down to Routing. This is where you set your Outbound Gateway to route mail to the Barracuda Email Security Gateway. Directly below that, add a route as shown.
  4. This is a REGEX expression containing your domain. Select Internal Email Host.

  5. Select Account Types to affect with this routing.

Now all internal mail is routed directly to Google servers, and all other mail routes through Outbound Gateway.

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