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How do I connect Google Workspace inboxes to ListKit Email Engine?

Written by Said Jrad
Updated over a week ago

THIS ARTICLE IS FOR: ✅ Self-Serve
Stage: Trial / Onboarding
Owner: OB
Last updated: 2026-03-12
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TL;DR

  • Google Workspace must trust the ListKit application before inboxes can connect.

  • Add the ListKit app in Google Workspace Admin → Configure new app.

  • Then connect the inbox in Email Engine → Inboxes → Connect Google Workspace inbox.

  • After connecting, the inbox is ready for warmup and sending.
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When you’d use this / Why it matters

Before ListKit can send campaigns from a Google Workspace inbox, Google must recognize the ListKit Email Engine as a trusted application.
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If this step is skipped, Google may show errors like:

  • “Google hasn’t verified this app”

  • inbox connection failures

  • blocked authentication

Completing this setup allows Email Engine to securely connect and manage your sending inboxes.
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Step-by-step

Step 1 - Open Google Workspace Admin

Go to:

https://admin.google.com/u/0/ac/owl/list?tab=configuredApps

Then click Configure new app.

Step 2 - Search for the ListKit App

In the search field, enter this ListKit Application ID:

850856172676-5qggac5a3sve2kiokloakrj2hih5muun.apps.googleusercontent.com

Then click Search.


The ListKit app will appear.

Click on the ListKit App and proceed with All Users.

Step 3 - Set the app as Trusted

When prompted, select Trusted.


Then continue to the next step and click Finish.

Once complete, you should now see the ListKit application listed as a configured app in your Google Workspace Admin account.

Step 4 - Connect your inbox inside Email Engine

Now go back to ListKit.

  1. Open Email Engine

  2. Click Inboxes

  3. Click Connect your Google Workspace inbox

Then follow all on-screen steps.

You’ll be asked to:

  • Sign in with Google

  • Continue the authentication flow

  • Allow the requested permissions

Once done, your Google Workspace inbox will be connected and ready to start warming up.

Important notes

1) Wait before connecting brand-new inboxes

If you recently created a new inbox on your domain, wait 6–12 hours before trying to connect it.

Trying to add it too soon may cause an error because Google may not have fully activated the mailbox yet.

2) This verification is only needed once

You only need to add the ListKit Application ID once per Google Workspace Admin account.

After that, future inboxes can be connected directly without repeating the app verification step.

3) If you see a Google security warning

If you still see an error like:

“Google hasn’t verified this app”

do not click Advanced and proceed without security. Double-check that:

  1. You connected the ListKit app to the correct Google Workspace Admin account

  2. You granted all required permissions

Expected outcome

Once the setup is completed successfully:

  • The ListKit app is trusted in Google Workspace

  • Your inbox is connected inside Email Engine → Inboxes

  • The inbox is ready to begin warming up and sending

Troubleshooting / FAQs

Why am I getting an error when connecting a new inbox?

If the inbox was created recently, wait 6–12 hours and try again. Google may not have fully activated it yet.

Do I need to configure the ListKit app every time I add a new inbox?

No. You only need to verify the ListKit app once per Google Workspace Admin account.

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