Email Deliverability: The Technical Setup Most Firms Get Wrong

You can write the best cold email in the world, but if it lands in spam, nobody will ever read it. Email deliverability is the unsexy foundation of outbound success, and most B2B service firms get it completely wrong.

Why Deliverability Matters More Than Ever

Google and Yahoo introduced strict sender requirements. Microsoft followed. The era of sending 500 cold emails per day from your main domain is over. If you do not have proper technical setup, your emails go to spam.

The Domain Strategy

Never send cold emails from your primary business domain. Buy two to three sending domain variations to protect your primary domain reputation.

DNS Authentication: The Big Three

SPF (Sender Policy Framework)

Tells receiving servers which IP addresses are authorised to send email for your domain.

DKIM (DomainKeys Identified Mail)

Adds a digital signature proving emails have not been tampered with in transit.

DMARC (Domain-based Message Authentication)

Tells receiving servers what to do with emails that fail SPF or DKIM checks. Start with p=none and graduate to quarantine or reject.

Domain Warming

New domains have zero reputation. Follow this schedule:

Week 1-2: Send 5-10 emails per day to engaged contacts

Week 3: Increase to 15-20 emails per day

Week 4: Increase to 30-40 per day

Week 5+: Gradually scale to your target volume (max 50-75 per domain per day)

Sending Limits and Best Practices

• Max 50-75 emails per domain per day for cold outbound
• Spread sends throughout the day
• Send during business hours in the recipient's timezone
• Monitor bounce rates — stay below 3%
• Remove hard bounces immediately

The Apollo.io Advantage

One reason I recommend Apollo.io for outbound is its built-in email verification. Before you add a prospect to a sequence, Apollo checks whether the email address is valid, reducing your bounce rate and protecting your sender reputation.

Recovery If You Are Already in Trouble

If your emails are landing in spam:

1. Stop all cold sending immediately
2. Check your DNS records — fix misconfigurations
3. Check blacklists — request removal if listed
4. Warm the domain again from scratch
5. Consider new domains if reputation is severely damaged

Deliverability is not a one-time setup. It requires ongoing monitoring and maintenance. But get it right, and every other part of your outbound system performs better.