Email Deliverability Guide: Get Your SaaS Emails to the Inbox

You can write the perfect email, but if it lands in spam, it's worthless. According to Mailchimp's deliverability research, SaaS companies with proper authentication see 20-30% higher inbox placement. Email deliverability—getting your messages to the inbox—is the foundation of successful email outreach.

This guide covers everything SaaS companies need to know about email deliverability, from technical setup to ongoing reputation management. For warm customer expansion campaigns, good deliverability is especially critical.

Understanding Email Deliverability

What is Deliverability?

Deliverability is the percentage of emails that reach the recipient's inbox (not spam, promotions, or blocked entirely).

Key Metrics:

How Email Filtering Works

Modern email providers use multiple signals to filter messages:

Sender Reputation Signals:

• Domain age and history
• IP address reputation
• Authentication (SPF, DKIM, DMARC)
• Historical spam complaints
• Engagement rates

Content Signals:

• Spam trigger words
• Link reputation
• HTML quality
• Image-to-text ratio
• Personalization

Recipient Signals:

• Prior engagement with sender
• Address validity
• Mailbox activity

Technical Setup

1. SPF (Sender Policy Framework)

SPF tells receiving servers which IPs are authorized to send email for your domain.

Setup: Add a TXT record to your DNS:

v=spf1 include:_spf.google.com include:sendgrid.net ~all

Components:

• v=spf1 - Version declaration
• include: - Authorize sending services
• ~all - Soft fail for unauthorized senders

2. DKIM (DomainKeys Identified Mail)

DKIM adds a digital signature to verify emails haven't been tampered with.

Setup:

1. Generate a public/private key pair
2. Add the public key to your DNS
3. Configure your email service to sign with the private key

DNS Record Example:

selector._domainkey.yourdomain.com TXT "v=DKIM1; k=rsa; p=MIGfMA0..."

3. DMARC (Domain-based Message Authentication)

DMARC tells receivers what to do with emails that fail SPF or DKIM.

Setup: Add a TXT record:

_dmarc.yourdomain.com TXT "v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com"

Policy Options:

• p=none - Monitor only (start here)
• p=quarantine - Send to spam
• p=reject - Block entirely

Implementation Path:

1. Start with p=none to collect reports
2. Analyze failures and fix legitimate sources
3. Move to p=quarantine
4. Graduate to p=reject

4. Reverse DNS (PTR Record)

Ensure your sending IP has a valid reverse DNS entry matching your sending domain.

5. Custom Tracking Domain

Use a custom tracking domain instead of shared tracking domains to protect your reputation.

Instead of: click.email-provider.com/track/...

Use: track.yourdomain.com/...

Domain and IP Reputation

Building Reputation

New domains and IPs have no reputation. Build it gradually:

Warming Schedule (New Domain):

Protecting Reputation

Do:

• Send to engaged recipients
• Clean your list regularly
• Monitor bounce rates
• Watch spam complaint rates
• Authenticate everything

Don't:

• Buy email lists
• Send to unengaged recipients
• Ignore bounces
• Use misleading subject lines
• Send without authentication

Monitoring Reputation

Tools:

• Google Postmaster Tools (Gmail reputation)
• Microsoft SNDS (Outlook reputation)
• MXToolbox (blacklist checking)
• Sender Score (aggregate reputation)

Content Best Practices

Avoid Spam Triggers

Problematic Phrases:

• "Act now!"
• "Limited time offer"
• "You've been selected"
• "Click here"
• "Free" (excessive use)
• ALL CAPS

Better Approach: Write naturally, as you would to a colleague. If it sounds like spam, it probably triggers spam filters.

HTML Quality

Good Practice:

• Clean, simple HTML
• Table-based layouts for compatibility
• Inline CSS
• Alt text on images
• Plain text alternative

Avoid:

• JavaScript
• Forms
• External CSS
• Attachments in cold emails
• Heavy image reliance

Link Hygiene

Best Practices:

• Use your domain for links
• Avoid URL shorteners
• Don't link to blacklisted domains
• Limit link quantity
• Include unsubscribe link

Personalization

Personalized emails have better engagement, which improves deliverability:

Personalization Elements:

• Recipient name
• Company name
• Relevant details
• Custom content blocks

Tools like AskUsers can generate deeply personalized content based on customer data.

List Management

Clean Your List

Remove addresses that hurt deliverability:

Validate Before Sending

Use email validation services:

• Syntax validation
• Domain verification
• Mailbox existence check
• Role-based detection
• Spam trap identification

Segmentation for Deliverability

Proper customer segmentation helps with deliverability. Send to engaged recipients first:

Engagement Optimization

Why Engagement Matters

Email providers track recipient behavior:

Positive Signals:

• Opens
• Clicks
• Replies
• Moving to primary inbox
• Adding to contacts

Negative Signals:

• No opens
• Spam complaints
• Unsubscribes
• Deleting without reading

Improving Engagement

Subject Lines:

• Be specific and relevant
• Create curiosity
• Keep under 50 characters
• Personalize when possible
• A/B test continuously

Send Timing:

• Test different days and times
• Consider recipient timezone
• Avoid sending at unusual hours
• Segment by engagement pattern

Content:

• Make it valuable
• Keep it concise
• Clear call to action
• Mobile-friendly formatting

Monitoring and Troubleshooting

Key Metrics to Track

Diagnosing Issues

Symptoms and Causes:

Recovery Steps

If you've been blacklisted or have reputation issues:

1. Stop sending - Pause to prevent further damage
2. Diagnose - Identify the cause
3. Clean - Remove problematic addresses
4. Fix - Address root cause
5. Request delisting - Apply to blacklists if necessary
6. Warm again - Gradually rebuild sending volume
7. Monitor - Watch metrics closely

Deliverability for Different Email Types

Transactional Emails

Higher priority, stricter standards:

• Separate from marketing sends
• Dedicated IP if volume justifies
• Immediate sends, no batching
• Critical content only

Marketing Emails

Moderate standards, engagement focus:

• Opt-in lists only
• Clear unsubscribe
• Value-focused content
• Regular cadence

Customer Outreach

Highest personalization, relationship-based. See our AI email personalization guide for advanced techniques:

• Individual sender (not "marketing@")
• Personal tone
• Relevant to recipient
• Conversation-starter

Tools and Resources

Email Service Providers

Deliverability Tools

• MXToolbox - Blacklist checking, DNS testing
• Mail-Tester - Email spam score analysis
• GlockApps - Inbox placement testing
• Validity - Comprehensive deliverability platform

Validation Services

• ZeroBounce - Email validation
• NeverBounce - List cleaning
• Kickbox - Real-time validation
• Hunter - Email verification

Conclusion

Email deliverability is both technical and behavioral. Get the technical foundation right (authentication, infrastructure), then focus on reputation management through good list hygiene and engaging content.

Key Takeaways:

1. Authenticate everything - SPF, DKIM, DMARC are non-negotiable
2. Build reputation gradually - Warm new domains and IPs
3. Clean your list - Remove bounces, unsubscribes, and inactive
4. Prioritize engagement - Send to engaged recipients first
5. Monitor continuously - Watch metrics and react quickly to issues

Start with a deliverability audit of your current setup, fix any gaps, and build processes to maintain good deliverability over time.

Frequently Asked Questions

How long does domain warming take?

Typically 4-8 weeks to build full reputation. Rush it and you'll trigger spam filters. Be patient with gradual volume increases.

Should I use a shared or dedicated IP?

Shared for low volume (<50K/month). Dedicated for high volume or when you need full control over reputation. Dedicated IPs require proper warming.

What's a good open rate to target?

20%+ for marketing emails, 40%+ for transactional. Customer outreach should aim for 30%+. Lower rates indicate deliverability or relevance issues.

Ready to improve your email outreach results? Try AskUsers to generate personalized customer emails with better engagement rates.