Introduction

If your cold emails keep landing in spam, you might be tempted to rewrite your subject lines or tweak your copy. But according to a recent the original LinkedIn post, the real culprit is often your sending infrastructure. The post argues that "Your email didn't land in spam because of your subject line. It landed there because of your IP's past." This insight shifts the focus from content to the technical foundation of your email program.

In this article, we'll explore why infrastructure is the first thing to check, common issues that hurt deliverability, and how to fix them.

Why Infrastructure Matters More Than Copy

Email filters have evolved. They no longer just scan keywords or links. They now evaluate the reputation of the IP address sending the email. If that IP has a history of abuse, spam complaints, or low engagement, your emails will be filtered regardless of how well-written they are.

As the LinkedIn post highlights, "An IP with a history of abuse before you ever touched it" can sink your deliverability. This is especially common when using shared IPs or purchasing aged domains. The previous sender's behavior becomes your problem.

Common Infrastructure Issues

1. Contaminated IP Reputation

When you use a shared IP pool, your reputation is tied to other senders on that IP. If a neighbor sends spam, your emails suffer. Even dedicated IPs can have a tainted past if they were previously used for questionable practices.

2. Ghost Servers Sending Mail in Your Name

Unauthorized servers sending email from your domain can damage your reputation. This often happens when email authentication records (SPF, DKIM, DMARC) are not properly configured. Attackers can spoof your domain, and if those emails get flagged, your domain's reputation takes the hit.

3. Subnet Contamination

Your IP is part of a larger subnet. If other IPs in that subnet have poor reputations, it can affect your deliverability. Filters sometimes look at the broader network neighborhood.

4. Lack of Proper Authentication

Google and Yahoo now require DMARC authentication for bulk senders. Without it, your emails are more likely to be rejected or marked as spam. DMARC helps you control who can send email on your behalf and provides visibility into unauthorized use.

How to Audit Your Email Infrastructure

Step 1: Check Your IP Reputation

Use free tools like MXToolbox, SenderScore, or Talos Intelligence to check your sending IP's reputation. Look for blacklists and historical data. If your IP is blacklisted, you'll need to request delisting and address the root cause.

Step 2: Verify Email Authentication

Ensure SPF, DKIM, and DMARC records are correctly set up for your domain. SPF specifies which servers can send email for your domain. DKIM adds a digital signature. DMARC tells receivers how to handle unauthenticated emails. Start with a monitoring policy (p=none) and gradually move to quarantine or reject.

Step 3: Review Your Sending Infrastructure

Check if any unauthorized servers are sending email using your domain. Look at your DMARC reports for sources you don't recognize. Remove any unknown IPs from your SPF record.

Step 4: Monitor Forwarding Rules

As noted in a related post, compromised email accounts often have hidden forwarding rules that silently copy emails to attackers. Regularly check your email settings for unfamiliar forwards or filters.

Step 5: Use Dedicated IPs or Clean Shared Pools

If you're on a shared IP, consider moving to a dedicated IP or a pool with strict sender policies. This gives you more control over your reputation.

Practical Steps to Improve Deliverability

  • Warm up new IPs gradually by sending low volumes and increasing over time.
  • Maintain a clean email list by removing inactive or invalid addresses.
  • Monitor bounce rates and spam complaints closely.
  • Use engagement-based sending: only send to recipients who have opened or clicked recently.
  • Implement a feedback loop with major ISPs to receive complaint data.

Conclusion

Before you rewrite another email, audit your infrastructure. The problem is often not your copy but the history and health of your sending IP. By addressing these foundational issues, you can significantly improve your inbox placement rates.

Remember: "Stop getting blamed for what the last sender did to your IP." Take control of your email infrastructure and watch your deliverability improve.