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How do I connect my own inboxes to Email Engine?

Written by Andre Haykal Jr

Using ListKit Bundles? Your Bundle's Google inboxes are added automatically after setup, so you don't need this article. Use it only to connect inboxes you already own. See What are ListKit's pre-warmed inboxes and how do I set them up?
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TL;DR

  • Campaigns need at least one connected inbox. Bundle inboxes connect automatically. Use this guide for inboxes you already own.

  • Open Inboxes in the left sidebar and click Connect inboxes.

  • Choose one of four connection methods (CSV, Google, Outlook, Other).

  • Once added, inboxes are ready for campaigns and the Master Inbox.
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Why this matters

Inboxes are the foundation of your Email Engine.
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Without connected sending inboxes, you cannot launch campaigns, send emails, or use the Master Inbox.
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Step 1: Open the Inboxes page

  1. Go to next.listkit.io and Login

  2. Click Inboxes in the left sidebar

You should now see the Inboxes page, where you can connect your sending accounts.
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Step 2: Choose how you want to add inboxes

On the Inboxes page, click Connect inboxes. You'll see four options:

  • CSV (Bulk Email Addition)

  • Google (Gmail / GSuite)

  • Outlook (Hotmail, Live, MSN) (also covers Microsoft 365 business mailboxes)

  • Other (Any provider, IMAP)

Choose the option that matches your email provider.

Option 1: Add inboxes using CSV (bulk upload)

Best for adding multiple inboxes at once.
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How to upload via CSV

  1. Click CSV Sample to download the required format.

  2. Follow the exact structure shown in the sample file.

  3. Click Upload.

  4. Select your completed CSV file.

  5. Click Continue.

The system will begin importing your inboxes.

What happens after upload?

You’ll see a summary screen showing:

  • Successfully added inboxes

  • Skipped inboxes (already exist)

  • Failed inboxes (errors in setup)

Review the results carefully.

Once complete, click:

Go to Inboxes

You should now see all successfully imported inboxes listed.

Option 2: Connect Google inboxes (Gmail / GSuite)

If you use Gmail or Google Workspace:

  1. Click Connect under Google

  2. Follow the authentication prompts

  3. Authorize ListKit to access the selected inboxes

After approval, your inboxes will appear automatically on the Inboxes page.
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Option 3: Connect Outlook inboxes (Hotmail, Live, MSN)

If you use Hotmail, Live, MSN or Microsoft 365 business mailboxes:

  1. Click Connect under Outlook

  2. Complete login and authorization

  3. Approve inbox access

Once authenticated, inboxes will be added automatically.
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Option 4: Connect any other provider (IMAP)

If you use another business email provider:

  1. Click Connect under Other (Any provider, IMAP)

  2. Enter your IMAP configuration details

  3. Complete the connection process

Once verified, the inbox will appear on the Inboxes page.
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Expected outcome

You should now see your connected inboxes listed on the Inboxes page.

They are now:

  • Warming up. Newly connected inboxes on new domains need 14 days of warmup before you send campaigns from them.

  • Ready to be Edited

  • Connected to the Email Engine
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Troubleshooting / FAQs

Why can’t I launch a campaign?
You likely haven’t added any inboxes yet. Campaigns require at least one connected sending inbox.
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Why was my inbox skipped?
It is already connected to your account.
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Why did my inbox fail to import?
There may be formatting issues in your CSV or incorrect credentials.
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Can I mix connection methods?
Yes. You can add some inboxes via Google Workspace and others via CSV or IMAP.

Should I use my own inboxes or ListKit's?
ListKit's data shows its pre-warmed inboxes average about 2.5x the reply rate of self-connected inboxes. If you have a Bundle, send from your Bundle inboxes. Connected inboxes also use your Bundle's sending allowance of 80,000 emails per billing period, which leaves room to send more than your Bundle inboxes alone.

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