Have you ever wondered why your outreach emails aren’t landing in inboxes? Maybe they’re ending up in spam, and you’re not sure why. One of the biggest reasons is using your main domain for outreach.
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When you send large volumes of cold emails from yourcompany.com, it can get flagged for spam. Worse, it could hurt the deliverability of all your business emails — even those to clients, partners, and employees.
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The solution? Use multiple domains and inboxes.
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With a simple setup, you’ll:
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✅ Protect your main domain's reputation so client emails aren't affected.
✅ Spread your email volume across inboxes to stay under email provider limits and avoid raising red flags.
✅ Avoid blacklisting since one flagged inbox or domain won’t ruin your entire strategy.
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In this guide, you’ll learn:
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1️⃣ What multiple domains and inboxes are.
2️⃣ Why they’re essential for outreach success.
3️⃣ How to set them up with tools like Zapmail.ai (the fastest, easiest option) and alternatives like Maildoso and Mailreef.
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Let’s break it down.

Here’s why this setup is non-negotiable if you’re serious about outreach.
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If you send bulk cold emails from yourcompany.com and they get flagged, your internal business emails might also end up in spam. This could damage your ability to communicate with clients, customers, and partners.
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With multiple domains, you create "sacrificial" outreach domains like tryyourcompany.com. If that domain gets flagged, your main domain stays 100% safe.
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Here’s a question to consider: How many emails does a typical person send per day?
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For the average person (who isn’t doing cold email), it’s definitely not 100+. In most cases, it’s probably 10-20 emails per day at most.
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Email providers (like Google) know this. If one of your inboxes suddenly sends 100+ emails in a day, that’s a red flag. This is why you need to spread your email volume across multiple inboxes.
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Instead of sending 100 emails from one inbox, you can send 10 emails from 10 different inboxes.
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Here’s what this looks like:

Why this works:

💡 Key takeaway: Sending 10-20 emails per day per inbox is much safer than sending 100 from one inbox.
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How many inboxes should you have?
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We recommend 2-3 inboxes per domain. This way, if one of your domains gets flagged, you still have other inboxes on other domains that are safe.
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If one of your inboxes gets flagged or blacklisted, it’s game over for that inbox. But with multiple domains and inboxes, one flagged inbox won't affect your entire outreach strategy. You'll have multiple fallback inboxes ready to go.
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Now that you know why it’s important, let’s get you set up. There are a few ways to do this, but the fastest, cheapest, and easiest option is Zapmail.ai (we have no affiliation - it's simply our favourite platform)
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Why Zapmail.ai is the Best Choice
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While there are other tools, Zapmail is the top choice because:

Zapmail is faster, cheaper, and more effective than setting up inboxes yourself.

Purchase custom domains directly in Zapmail (no need for a separate domain provider). Examples:

Once you buy them, Zapmail connects them to your inboxes and sets up SPF, DKIM, and DMARC automatically.
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1️⃣ Add the custom domains you purchased.
2️⃣ Set up inboxes like:

Zapmail automates the entire process, so you don’t have to deal with DNS records.

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For credibility, add profile pictures for each inbox.
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With domain forwarding, visitors to tryyourcompany.com can be redirected to your main website yourcompany.com.
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Now that your domains and inboxes are set up, it’s time to warm them up properly so your emails actually land in inboxes (not spam folders). Warming up inboxes is one of the most critical steps to ensure strong deliverability.
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👉 Next Article: How to Warm Up Your Inboxes for Better Deliverability

Don’t skip this step — it’s essential for boosting your email performance!