Your emails are going to spam. It's frustrating, but there's always a reason. Understanding the factors that affect deliverability is the first step to solving the problem.
How Email Delivery Works
When you send an email, it doesn't go directly to the inbox. It passes through several checkpoints: your SMTP server sends it, the recipient's server receives it, then authentication checks, reputation checks, content analysis, and engagement signals all determine where your email lands.
The Three Pillars of Deliverability
1. Authentication
The first thing receiving servers check. Does your domain have proper SPF, DKIM, and DMARC records? Is your sending IP authorized? Does the IP have a valid PTR record?
If any of these fail, your email is immediately at a disadvantage. We covered authentication setup in detail in our SPF, DKIM, and DMARC guide.
2. Reputation
Both your sending IP and your domain have reputation scores tracked by ISPs. Factors include sending volume and consistency, bounce rates, spam complaint rates, how long the IP/domain has been sending, and blacklist status.
Reputation is built over time and can be destroyed in minutes with a bad send.
3. Content
Even with perfect authentication and reputation, bad content triggers spam filters. Common red flags include spam trigger words ("FREE!!!", "ACT NOW"), too many links, heavy image-to-text ratio, missing unsubscribe link, and misleading subject lines.
Why Engagement Matters Most
Increasingly, ISPs weigh engagement signals above everything else. They track whether recipients open your emails, reply to them, click links, or mark them as spam.
High engagement tells ISPs your emails are wanted. Low engagement tells them the opposite. This is why sending to disengaged contacts actually hurts your deliverability with engaged contacts too.
Quick Diagnostic Steps
- Check your authentication with smtpcheck.lexlabtools.com
- Verify your email addresses with emailverify.lexlabtools.com
- Review your bounce and complaint rates
- Check if your IP is on any blacklists
- Look at your email content for obvious spam triggers
If these checks reveal issues, a professional deliverability audit can pinpoint exactly what's wrong and provide a clear remediation plan.
