How to Add an Inbound Mail Gateway in Google Workspace

Quick and easy-to-follow guide for Google Workspace administrators

What is an inbound mail gateway

An inbound mail gateway is an email server that your incoming messages pass through before delivering to the final recipient.

When to set up the Inbound gateway setting

Let’s say your domain is set up to receive emails at another service first and then pass along an exact copy to Google’s mail servers.
For example, this is the case when you set up Dual delivery with another email service as the initial recipient of emails to your domain and Google Workspace as the secondary recipient.
In this case, you need to point your MX records to the other service and add the service to your Inbound Gateway setting in Google Workspace.

How the Inbound gateway works

Google trusts the inbound gateway server, skips checking it for authentication, and allows emails through.

How to set up an Inbound gateway in Google Workspace step-by-step with images

Step 1

In the Admin console at https://admin.google.com, click the Apps icon.

Step 2

Select Google Workspace.

Step 3

Click Gmail. Make sure not to check the box to the left; just click the service.

Step 4

Select Spam, Phishing and Malware.

Step 5

Under Organizational Units, select the OU with the users whose settings you want to update. The same updates will apply to all sub-OUs under the OU you choose.

By default, if you don’t select an OU, you will add your setting to the top OU, named after your domain. This way, you will apply changes to all users in your account. This is generally recommended in this case.

If you’re not familiar with OUs, click here.

Step 6

Click the Inbound Gateway setting.

Step 7

Check the Enable box to turn it on.

Add gateway IP addresses

Next, click the ADD button under IP addresses/ranges, type the IP addresses or ranges, and click SAVE.

Optionally, check the box ‘Automatically detect external IP’ – this helps the setting work better.

You may also wish to Reject all mail from non-gateway IPs and require a secure TLS connection from the gateways. This is optional but recommended if you need to ensure that all messages get encrypted for safe delivery.

Step 8

Message tagging

Under 2. Message Tagging, you can set up messages from the gateway to be treated as spam if the header matches a regexp. You can learn more about regexp in Google’s Help Center.

Optionally, you can check the box below to turn off Gmail’s built-in spam filters and only rely on the header value above to classify messages as spam.

Click SAVE. It may take up to 24 hours for it to start working.

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Add Non-Google Email Services (Hosts)

Add another mail service to your Google Workspace settings.

Get Emails in Multiple Email Services Simultaneously (Dual Delivery)

Get your emails delivered both to Google Workspace and another mail service at the same time.

Split Your Incoming Email Delivery Between Multiple Email Services (Split Delivery)

Have your emails delivered to Google Workspace if the receiving email address exists in Google Workspace, otherwise deliver them to another mail service.

Apply Google Workspace Settings to Third-Party Email Services (Non-Gmail Mailbox)

Set this up if you have another mail service and don’t want to receive mail at Google but still want to use Google Workspace email settings like spam filtering and routing.

Store Emails You Send From Third-Party Services in Gmail (Comprehensive Mail Storage)

Save a copy of all sent/received mail by non-Gmail mailboxes in users’ Gmail mailboxes as a backup.

Route Emails You Send From Another Email Service Through Google (SMTP Relay)

Have emails sent from another mail server go through Google Workspace before delivery.

Set up an Inbound Mail Gateway

Have your incoming emails go through another mail server before they get delivered to Gmail.

Set up an Outbound Mail Gateway

Have emails sent from Google Workspace go through another mail server before delivery.

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