The 5 Keys to Cold Email Deliverability (Without Getting Burned)

If you're running outbound campaigns, there's one thing that'll kill your results faster than bad copy: poor deliverability.

You could have the best messaging in the world, but if your emails aren't landing in the inbox, you're invisible.

In this post, I'm breaking down everything we've learned at Danish Lead Co. about cold email deliverability—from infrastructure to content—so you can avoid the traps that most B2B teams fall into.

1. Nail Your Email Infrastructure

Before you send a single email, your setup needs to be airtight.

We recommend using reputable domain providers like Squarespace, GoDaddy, or Porkbun. Buy domains that look legitimate and keep them diversified across providers.

Once you have your domains:

• Set up 2 email accounts per domain

• Split between platforms (Gmail, Outlook) to avoid putting all your eggs in one basket

• Properly configure DNS records: DKIM, SPF, custom tracking domains (especially if using tools like Instantly or Smartlead)

"Everything keeps changing. You have to diversify so you’re always getting positive replies."

If you're setting up at scale (15+ domains), limit it to 5 domains and 10 email accounts per IP or browser to reduce flagging risk.

2. Control Sending Volumes to Mimic Human Behavior

This is where a lot of teams blow it.

Don’t blast 100 emails per day per account.

We’ve tested this across dozens of campaigns: 35-40 emails per account per day is the current sweet spot.

Keep bounce rates under 2-3%. And aim for a combined reply rate of 20-30% per email account.

Not getting enough replies from your campaigns? Use warm-up emails through Smartlead or Instantly to artificially boost the reply rate and protect your sender reputation.

Quick math example:

• 15 campaign emails/day @ 10% reply rate

• 25 warm-up emails/day @ 50% reply rate

• Overall: ~30% reply rate across that account

3. Write for Deliverability (Not Just Persuasion)

Most people obsess over copywriting… but forget about the words that get you flagged.

Here’s how to stay under the radar:

• Use Spintax (especially if sending 20,000+ emails/month)

• Spin at the sentence level, not just single words

• Use ChatGPT to generate variations—but always double-check that it still sounds natural

• Avoid spam trigger words (like “offer,” “call”, etc.)

Use Smartlead’s built-in spam checker (or an external one) to screen your content before launch.

4. Target Smarter, Not Broader

Deliverability isn’t just a technical game. It starts with sending to the right people.

Clean data = fewer bounces, more replies.

We use tools like MillionVerifier or NeverBounce to verify emails. If you’re working with catch-all domains, run them through Scrubby before sending.

Pro tip: Only send to work emails. Personal inboxes (Gmail, Hotmail) have stricter spam rules and a higher risk of getting flagged.

5. Monitor and Rotate Regularly

Even with perfect setup, you’ll eventually hit snags.

That’s why we recommend weekly or biweekly blacklist checks.

If a domain gets blacklisted, don’t try to resuscitate it. Trash the account, buy a new domain, and trace what caused it so you don’t repeat the mistake.

A quick inbox test (send emails to yourself) can also help spot spam issues early.

"If you’re flagged, stop sending immediately. Swap out fast before it tanks your entire system."

Want help building a cold email system that stays out of spam and lands deals? 

Book a meeting with my co-founder Martin here.