Email Deliverability 101: Staying Out of Spam

Best practices for list hygiene, DKIM/SPF records, and content optimization to ensure your emails reach the inbox.

You've crafted the perfect email campaign, but none of it matters if your messages end up in spam. Email deliverability is the foundation of successful email marketing, yet it's often overlooked until problems arise.

Understanding Email Authentication

Email authentication protocols prove to receiving servers that your emails are legitimate. There are three main protocols you need to configure:

SPF (Sender Policy Framework)

SPF specifies which mail servers are authorized to send emails on behalf of your domain. Without it, spammers could send emails pretending to be from your domain.

DKIM (DomainKeys Identified Mail)

DKIM adds a digital signature to your emails that proves they haven't been tampered with in transit. It's like a wax seal on a letter.

DMARC (Domain-based Message Authentication)

DMARC tells receiving servers what to do when SPF or DKIM checks fail. It also enables reporting so you can monitor authentication issues.

"Setting up proper email authentication isn't optional anymore—it's table stakes for any serious email marketer."

List Hygiene Best Practices

A clean email list is essential for maintaining good deliverability. Here's how to keep yours healthy:

• Remove hard bounces immediately: These are permanent delivery failures that hurt your sender reputation.
• Re-engage inactive subscribers: Send a win-back campaign before removing cold contacts.
• Use double opt-in: Confirm new subscribers really want to receive your emails.
• Never buy email lists: Purchased lists have high bounce rates and spam complaints.
• Honor unsubscribes instantly: Make it easy to opt out and process requests immediately.

Content Optimization Tips

What you say and how you say it can trigger spam filters. Follow these guidelines:

• Avoid spam trigger words like "FREE," "ACT NOW," "LIMITED TIME"
• Maintain a healthy text-to-image ratio (60% text, 40% images)
• Include a plain text version of your HTML emails
• Personalize your subject lines and content
• Keep your "From" name consistent and recognizable

Monitoring Your Sender Reputation

Your sender reputation is like a credit score for email. Key metrics to watch:

• Bounce rate: Keep below 2%
• Spam complaint rate: Keep below 0.1%
• Open rate: Monitor for sudden drops

PostDog includes built-in deliverability monitoring that alerts you to potential issues before they become problems. Start your email campaigns on the right foot with proper authentication and list management from day one.