Cold Email isn’t the Problem. Your Infrastructure is.

Cold emailing used to be pretty simple. You’d write a quick pitch, press send, and most of the time, your message would show up in someone’s inbox. That was it. All you really needed was a Gmail tab, a list in a spreadsheet, and a bit of follow-through. If you were lucky, you’d even get a few replies before your first coffee.
These days? Not so much. Things have changed a lot. Now, sending cold emails feels more like threading a needle. Writing a clever message isn’t enough anymore. Spam filters have gotten way more aggressive, inbox providers are a lot pickier, and the rules seem to change all the time. What used to work just doesn’t really do the job now.
So it might not be your copy if you’re not getting replies, or if your emails aren’t even showing up. The issue is usually what’s going on behind the scenes. Most of the time, it’s the technical setup that quietly blocks your message from ever being seen.

Why Cold Email Used to Work

There was a time when sending cold emails was simple. You could use your main domain without warming it up, and your messages would still land in inboxes. Inbox providers weren’t too strict, and getting delivered didn’t take much effort. SPF, DKIM, and DMARC weren’t even on most people’s radar.
The usual setup back then was straightforward: one sales rep, one mailbox, and one seat in your outreach tool. You could send 150 to 200 cold emails per day from that single setup. DNS settings were basic. There was no deliverability monitoring, no domain rotation, and no need to manage complex infrastructure. It just worked.
Tools were simple, but effective. Back then, it really just came down to saying something that made sense to the right person. If the message was simple and it landed with someone who actually needed it, chances are they’d write back.
But that kind of cold email? It doesn’t really work anymore. Things have moved on.

The quiet shift that’s making cold outreach harder than ever

Cold email used to feel like a hidden gem. Then suddenly everything changed.
Things started to shift when cold email platforms introduced full automation for around $100 a month. What used to take hands-on effort could suddenly be done at scale with almost no oversight. To sweeten the deal, platforms stopped charging by user seat and started billing based on sending volume. At first, it seemed like the perfect setup.
That illusion didn’t last long.
Lowering the barrier to entry meant a flood of new senders entered the space. As inboxes filled up with outreach emails, major providers like Google and Microsoft began tightening their defenses. Spam filters evolved, and the bar for what qualifies as a legitimate message got higher.
Microsoft's gotten a lot harder to deal with lately. If you’ve been reaching out to larger companies that use Outlook, you’ve probably run into this. Getting into their inboxes isn’t easy. Their spam filters are strict, and it takes more than just a solid message to get through.
Google brought its own challenges. The removal of open tracking was a huge blow for senders. It used to offer insight into whether emails were even being seen. Now it’s gone. Worse still, trying to track opens today can actually damage your deliverability. That tiny pixel you once depended on is now more of a red flag than a helpful tool.
And those are just the visible changes. In the background, dozens of quiet updates have rolled out. Tweaks to rules, server settings, and spam detection logic have made it harder to predict what will land and what won’t. These changes tend to roll out quietly, without any clear notice or explanation. That leaves most people guessing, which just adds to the confusion around cold outreach.
If your emails aren’t getting opened or worse, not even making it to the inbox. The problem might have nothing to do with your message at all. The real issue could be the system behind it. Deliverability now depends just as much on your infrastructure as it does on your content.
Cold email isn’t dead. But if you want real results today, you have to understand the new rules and play smart.

How to Beat SPAM Filters

Let’s be honest, cold email isn’t that easy anymore. It used to be pretty straightforward. You’d send out a few messages and hope for replies. These days, it’s not just about writing something good. If your setup’s not right, your emails probably won’t even get seen.
So, how do we actually beat the spam filters?
Here’s how people are getting their emails through and what you can do to make it work.

Diversify Your Infrastructure

Before anything else, protect yourself by spreading out your sending volume. This means building an infrastructure that’s stable, flexible, and not tied to one single domain or provider.
Here’s how to do it:

• Use multiple domains and mailboxes to split your sending volume. If one domain gets flagged, your whole outreach won’t crash.
  
  
• Never send from your main domain. It’s too risky. One bad campaign and your entire brand reputation could be damaged.
  
  
• Set things up across different email platforms. Don’t depend only on Google. Using a mix of providers helps spread your sending and makes your deliverability safer.
  
  
• Stick to low sending limits. Keep it to around 10 to 15 real cold emails per mailbox per day.
  
  
• Monitor and rotate regularly to catch issues early and avoid long-term deliverability damage.

Know Your Numbers

Before scaling any outreach, you’ve got to stop and look at the numbers. Otherwise, you’re just guessing. So here’s a quick example to figure out how many emails you might actually need.
Let’s say the goal is 50 Marketing Qualified Leads for the month. That’s what you’re shooting for.
Now, based on what you know:
Reply rate is 4%
Conversion from reply to MQL is 10%
So if you're aiming for 50 MQLs, here's what that would take:
50 MQL divided by the conversion rate of 10% is equal to 500 replies
So, if you take those 500 replies and divide them by a 4% reply rate, you end up needing to reach around 12,500 contacts.
Now think about this, you're planning to send 4 emails to each one. That’s your first message, plus three follow-ups to try and get a response.
If you’re reaching out to 12,500 contacts, that adds up fast. Multiply that out and you’re at about 50,000 emails total.
That’s what it’ll probably take to get your 50 MQLs. Not a small send, but that’s the math.

Plan Your Domains and Mailboxes

Now that you’ve got your target volume, it’s time to set up the right number of mailboxes and domains.
Here’s the golden rule:

• 1 mailbox = 15 cold emails per day or less
  
  
• 1 domain = 3 mailboxes

That means:
1 domain = 45 cold emails per day
For 50,000 emails per month, you’ll need:

• Around 50 domains
  
  
• At least 112 mailboxes

Also, don’t forget to factor in about 20% extra for rotation. These are backup mailboxes that stay warmed up but aren’t sending. You’ll need them on standby in case your main pool runs into deliverability issues or gets flagged.

Don’t Rely on Just One Email Provider

Running your entire cold outreach through a single platform is risky. One policy change or deliverability issue could bring everything to a halt. A smarter move is to distribute your sending across multiple providers.
With Mailpool, you don’t have to set it up manually. It automatically creates mailboxes and handles all the technical stuff in just a few clicks.

Launch Clean, SPAM-Safe Campaigns

Even the best infrastructure can fall apart if your campaigns are sloppy. Here’s how to stay on the safe side:

• Stick to plain text emails for your initial message
• Avoid heavy formatting, images, and tracking pixels
• Use CNAME-based link tracking to protect your domain reputation
• Write clear, human messages, don’t trigger SPAM filters with hype or gimmicks
• Follow hygiene rules like rotation and daily send limits

Monitor Everything and Rotate Smartly

Deliverability issues are rarely obvious at first. If you want to catch problems early, you need proper monitoring in place.

• DMARC reporting to track DNS health
• Inbox placement testing to check how you’re doing across your email providers
• SPAM alerts so you know the moment something needs attention

If you notice a drop in performance, rotate your infrastructure. That’s where your extra 20% of warmed-up mailboxes come in. Swap out anything underperforming and recover it behind the scenes.
If you want to beat spam filters, forget the shortcuts and quick fixes. What really works is building your setup the right way from the beginning. That means keeping your infrastructure clean, spreading out where and how you send, sticking to proven best practices, and staying on top of things with solid monitoring and regular rotation. The teams that consistently land in the inbox are the ones treating email like an infrastructure game, not just a copywriting one.
Get that right, and spam filters won’t stand a chance.

So, who should be handling the cold outreach infrastructure?

Ideally, it’s someone who understands both the technical side (like DNS records, deliverability, domain health) and the strategic side (like reply rates, targeting, messaging). But in most companies, that person doesn’t exist.
Here's what usually happens:
Sales wants leads, but they don’t set up inboxes or monitor spam filters.
IT can configure things, but doesn’t track performance or care about reply rates.
Growth drives strategy, but usually lacks the time or skills to manage infrastructure.
So it falls between the cracks, until deliverability drops, replies stop coming in, and no one knows why.

Should you worry about it if your goal is growth?

Absolutely. If cold outreach is part of your pipeline strategy, then your infrastructure is your foundation. Without a solid setup, even the strongest copy and best targeting won’t make a difference. Your emails simply won’t reach the inbox.
That’s where services like Mailpool come in. They give growth teams the technical support they need to scale outreach without running into deliverability issues.

Everything You Need for Outreach, Set Up, and Ready to Go

Setting up cold email the right way can eat up a lot of time, especially if you’re trying to figure it all out on your own. Mailpool takes the pressure off by handling the messy parts for you. It automates domain purchase in bulk and keeps everything organized, so you're not stuck juggling things one by one. Need inboxes on Google Workspace, Outlook, or even through Mailpool? You can have everything set up quickly without having to deal with confusing settings. And when it comes to the technical parts like SPF, DKIM, and DMARC, Mailpool takes care of all of it quietly in the background. You don’t need to mess with DNS at all. It even sets up email forwarding, so keeping track of replies is simple and doesn’t involve jumping between accounts. Once everything’s in place, the system just works.
Cold email isn’t the problem. It just takes more work than it used to. A few years ago, you could send from one inbox and expect replies. These days, it’s a different game. If your emails aren’t landing, the issue probably isn’t your message. It’s your setup. The teams getting results now are the ones that treat deliverability as part of the strategy from the start. With Mailpool, your infrastructure is built the right way from day one. No more guessing, putting out fires. Just a system that’s ready to scale when you are.