Restricting Email Communication to One Domain in Google Workspace (Gmail)

Objective

Allow cart@example.in to send and receive emails only with the domain icicibank.com. Block all other inbound and outbound email communication.

Steps to Configure in Google Admin Console

1. Login

2. Open Gmail Settings

  • Navigate to: Apps → Google Workspace → Gmail → Compliance

INBOUND Restriction (Receiving emails)

3. Add a Routing Rule

  • Scroll down to Routing section.

  • Click “Configure” (or “Add Another” if rules already exist).

Name: Allow inbound only from icicibank.com (cart@example.in)

Emails to affect:

  • Choose Inbound, Internal - receiving, and Outbound (optional) if needed.

Envelope recipient:

  • Specify → cart@example.in

Add Expression:

  • If the sender’s domain is not → icicibank.com

Action:

  • Reject the message.

  • Add a custom rejection notice, e.g. "This mailbox only accepts messages from @icicibank.com."

Save the rule.

OUTBOUND Restriction (Sending emails)

4. Create another rule under Outbound

  • Go to: Apps → Google Workspace → Gmail → Compliance

  • Scroll down to “Outbound” section and click “Configure”.

Name: Allow outbound only to icicibank.com (cart@example.in)

Emails to affect:

  • Choose Outbound and Internal - sending.

Envelope sender:

  • Specify → cart@example.in

Add Expression:

  • If the recipient’s domain is not → icicibank.com

Action:

  • Reject the message.

  • Add a rejection notice, e.g. "This mailbox is restricted to send only to @icicibank.com domain."

Save the rule.

5. Verify & Test

  • From cart@example.in, send:

    • ✅ To user@icicibank.com → should succeed.

    • ❌ To user@gmail.com → should be rejected.

  • From an external account:

    • ✅ From user@icicibank.com → should arrive.

    • ❌ From user@yahoo.com → should be rejected with your custom message.

Summary Table

Direction
Allowed Domain
Blocked
Affected User

Inbound

@icicibank.com

All others

cart@example.in

Outbound

@icicibank.com

All others

cart@exmaple.in

Notes & Best Practices

  • These rules apply only to the specified user (cart@example.in).

  • Be careful if multiple routing rules exist — Google Workspace processes them in order.

  • Always save and test after changes.

  • Consider documenting the setup for audit purposes.

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