Not getting replies? Landing in spam? If you’re sending cold emails or running any kind of outreach, you know deliverability is the name of the game. This guide is for folks who want to stack the odds in their favor by connecting multiple inboxes to Warmupinbox, not just one. We’ll walk through how to set this up, what actually works, and what’s just hype—without wasting your time.
Why connect more than one inbox?
Let’s get this out of the way: one inbox, warmed up, can absolutely help, but it’s not a silver bullet. If you’re sending real volume or want to hedge your bets, multiple inboxes spread the risk and let you:
- Send more emails safely (no single inbox gets flagged for suspicious activity).
- Avoid putting all your eggs in one basket—if one inbox gets throttled or blacklisted, others keep going.
- Make your warming process look more organic.
But don’t get greedy: Adding a ton of inboxes just to send junk faster won’t fool anyone (especially Google or Microsoft). More isn’t always better.
What is Warmupinbox, really?
Warmupinbox is a tool that tries to make your inbox look “normal” to spam filters. It does this by sending and receiving emails with other inboxes in its network, marking them as important, and pulling them out of spam if needed. The idea is to show the big email providers that you’re not a bot or a spammer.
Does it work? It helps—especially if you’re starting with a fresh domain or a new inbox. But don’t expect miracles. If your emails are garbage or you’re blasting 1,000 strangers a day, no warmup tool will save you.
Step 1: Decide how many inboxes you actually need
Before you start connecting everything with a login and a pulse, figure out your real needs.
Ask yourself:
- How many emails do you actually send per day, per inbox?
- Are you splitting campaigns by rep, region, or product?
- Do you care more about volume, or just redundancy?
Some honest numbers: - 1-2 inboxes: Fine for small teams or low-volume outreach. - 3-5 inboxes: Good for moderate volume, or if you want backup options. - 6+ inboxes: Only go here if you know what you’re doing. More complexity, more things to track.
Pro tip: Don’t overcomplicate. Warm up what you need, not what looks impressive on a dashboard.
Step 2: Prep your inboxes
Before connecting anything, make sure your inboxes are ready to be warmed up.
Set up proper DNS records
This is non-negotiable. If your DNS (SPF, DKIM, DMARC) isn’t set up right, you’ll end up in spam no matter what. Most ESPs (Google Workspace, Outlook, Zoho, etc.) have guides on setting these up.
- SPF: Proves your inbox is allowed to send for your domain.
- DKIM: Adds a digital signature.
- DMARC: Tells recipients how to handle suspicious messages.
Skip this, and you’re wasting your time.
Create real, human-like accounts
- Use real names and profile photos.
- Fill out signatures and basic info.
- Send a couple of manual emails to real people (just to make it look natural).
If you connect a blank, obviously-fake inbox, the warmup network won’t do much for you.
Step 3: Connect your inboxes to Warmupinbox
Here’s the no-nonsense way to connect multiple inboxes:
- Sign in to your Warmupinbox account.
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If you’re new, sign up. Paid plans are required for multiple inboxes.
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Go to the “Inboxes” section.
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Usually a dashboard or sidebar menu.
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Click “Add Inbox” or similar.
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You’ll be prompted to choose your provider (Google, Microsoft, custom IMAP/SMTP, etc.).
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Authenticate each inbox.
- Use OAuth if possible (safer, easier).
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For IMAP/SMTP, you’ll need server info and app passwords. Don’t use your main login for security.
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Repeat for each inbox you want to add.
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Take your time. Rushing = mistakes, which means broken connections or, worse, security headaches.
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Check connection status.
- Warmupinbox should show each inbox as “Active” or similar. If there are errors, fix them before moving on.
A few things to keep in mind:
- Don’t connect inboxes you don’t control. Sharing access to random inboxes is a security risk.
- Space it out. Connecting 10 inboxes in 10 minutes looks weird (to both Warmupinbox and your email host).
- Monitor sent mail limits. Some providers throttle new inboxes, so don’t expect to send 100/day right away.
Step 4: Set up and manage the warmup process
Once your inboxes are connected, you’ll need to configure how they warm up. Here’s what matters:
Choose realistic warmup settings
- Start slow. 1–5 emails per day per inbox is plenty at first.
- Ramp up gradually. Increase by a couple of emails a day, not by dozens.
- Don’t max out settings. Just because the slider lets you, doesn’t mean you should. Looking “too active” too fast is a red flag.
Use the right volume per inbox
- Google and Microsoft are especially strict with new inboxes on new domains.
- If you’re using aged domains, you can ramp up a bit faster, but still: don’t get greedy.
Monitor reports
- Warmupinbox gives you stats: how many emails sent, deliverability, spam rate, etc.
- If you see a spike in spam placements, pause and investigate. Sometimes it’s your content, sometimes your DNS, sometimes just bad luck.
Ignore: - Overly optimistic dashboards (100% deliverability is not real life). - Any “magic” feature that claims to get you into inboxes with zero effort.
Step 5: Keep your inboxes healthy—don’t just set and forget
Connecting multiple inboxes is only half the battle. Here’s how to keep things running smoothly:
Regularly check deliverability
Send test emails (using tools like Mail-Tester or just your own Gmail) to see where your emails land. If you’re hitting spam, don’t panic—figure out why.
Rotate sending
Don’t use every inbox for every campaign. Mix things up. If one inbox starts having issues, pull it out of rotation and let it recover.
Watch for provider warnings
Google and Microsoft will warn you if you’re pushing limits. Pay attention to those emails—they’re not just for show.
Don’t share inboxes across tools
If you’re using other sending or automation tools (like Mailshake, Lemlist, etc.), make sure you’re not sending from the same inbox at the same time via multiple tools. That’s a recipe for throttling.
What actually works (and what doesn’t)
Works: - Warming up inboxes slowly and naturally. - Using real content and replying to some warmup emails manually. - Keeping DNS records spotless.
Doesn’t work: - Connecting a bunch of burner inboxes and expecting them all to stick. - Using broken or fake profile info. - Blasting cold emails before warmup is done.
Ignore: - “AI” deliverability promises. - Any tool that asks for your main email password (always use OAuth or app-specific passwords). - Gimmicks like sending only images or random gibberish to look “human.” Spam filters are smarter than that.
Troubleshooting common issues
- Connection errors: Double-check credentials, enable IMAP, and make sure app passwords are used if your provider requires it.
- Spam placements during warmup: Check your template, DNS, and whether you’re using blacklisted domains or IPs.
- Provider lockouts: If you get locked out, stop all sending and review your provider’s security alerts.
Wrap-up: Keep it simple, stay patient
If you want better deliverability, connecting multiple inboxes to Warmupinbox can help—but only if you do it the right way. Don’t overthink it: set up a few, warm them up slow, watch your stats, and keep your DNS tight. Most importantly, don’t fall for shortcuts. Smart, steady warming beats brute force every time. Iterate as you go, and don’t be afraid to cut what isn’t working.