Transactional

Deliverability Best Practices

Tips and techniques to maximize your email deliverability.

Overview

Deliverability is the ability to reach recipients' inboxes. Poor deliverability means your emails land in spam folders or aren't delivered at all.

Authentication

SPF (Sender Policy Framework)

SPF tells receiving servers which IPs can send for your domain:

v=spf1 include:spf.usetransactional.com ~all

Tips:

  • Only one SPF record per domain
  • Keep within 10 DNS lookup limit
  • Use ~all (softfail) or -all (hardfail)

DKIM (DomainKeys Identified Mail)

DKIM adds a digital signature to your emails:

Host: transactional._domainkey
Value: v=DKIM1; k=rsa; p=MIGf...

Tips:

  • Use 2048-bit keys minimum
  • Rotate keys periodically
  • Don't modify signed headers

DMARC (Domain-based Message Authentication)

DMARC sets policy for failed authentication:

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

Policy levels:

  • p=none - Monitor only
  • p=quarantine - Send to spam
  • p=reject - Block delivery

Tips:

  • Start with p=none to monitor
  • Review reports before enforcing
  • Gradually increase to p=reject

List Hygiene

Collect Emails Properly

  • Use double opt-in for new subscribers
  • Validate email format on input
  • Check MX records before accepting

Clean Regularly

  • Remove hard bounces immediately
  • Prune inactive subscribers (no opens in 6+ months)
  • Re-engage before removing

Never Buy Lists

Purchased lists lead to:

  • High bounce rates
  • Spam complaints
  • Blacklisting
  • Legal issues

Content Best Practices

Subject Lines

Do:

  • Keep under 50 characters
  • Be specific and relevant
  • Create urgency naturally

Don't:

  • Use ALL CAPS
  • Use excessive punctuation!!!
  • Use spam trigger words (FREE!!!, Act now!)

Body Content

Do:

  • Maintain good text-to-image ratio (60/40)
  • Include plain text version
  • Use recognizable sender name
  • Include physical address (required by law)

Don't:

  • Use link shorteners
  • Embed forms
  • Use JavaScript
  • Use tiny or hidden text

Links

Do:

  • Use full URLs
  • Link to reputable domains
  • Use descriptive anchor text

Don't:

  • Use URL shorteners
  • Link to suspicious domains
  • Use too many links

Sending Practices

Warm Up New IPs/Domains

Gradually increase sending volume:

WeekDaily Volume
150-100
2200-500
31,000-2,000
45,000-10,000
5+Full volume

Maintain Consistent Volume

  • Avoid sudden spikes
  • Send regularly, not in bursts
  • Scale gradually

Segment Your Audience

  • Send to engaged users first
  • Separate transactional from marketing
  • Target based on behavior

Monitoring

Key Metrics

MetricHealthyWarningCritical
Bounce Rate< 2%2-5%> 5%
Complaint Rate< 0.1%0.1-0.3%> 0.3%
Open Rate> 20%10-20%< 10%
Spam Trap Hits01-2> 2

Monitor Blacklists

Check if your domain/IP is listed:

Review Postmaster Tools

Engagement

Improve Open Rates

  • Optimize subject lines
  • Send at optimal times
  • Segment by engagement

Reduce Complaints

  • Make unsubscribe easy
  • Honor preferences
  • Set expectations at sign-up
  • Don't send too frequently

Re-engagement Campaigns

Before removing inactive subscribers:

  1. Send "We miss you" email
  2. Offer incentive to stay
  3. Ask for feedback
  4. Give clear unsubscribe option
  5. Remove if no response

Technical Infrastructure

Dedicated IP

Consider a dedicated IP if you send > 100k emails/month:

Pros:

  • Full control of reputation
  • No shared reputation risk
  • Better deliverability (if managed well)

Cons:

  • Requires warm-up
  • Your reputation only
  • Higher cost

Custom Tracking Domain

Use your own domain for tracking:

  • Improves trust
  • Avoids third-party blocklists
  • Better brand consistency

Return-Path Domain

Align your return-path (bounce address) with your from domain.

Troubleshooting

Emails Going to Spam

  1. Check authentication (SPF, DKIM, DMARC)
  2. Review content for spam triggers
  3. Check blacklists
  4. Verify sender reputation
  5. Review engagement metrics

High Bounce Rate

  1. Validate email addresses
  2. Clean your list
  3. Check for typos
  4. Verify domain exists

Low Open Rates

  1. Optimize subject lines
  2. Check sender name recognition
  3. Review send timing
  4. Segment by engagement
  5. Check spam folder placement

Compliance Checklist

  • Include physical address
  • Provide unsubscribe link
  • Honor unsubscribe requests within 10 days
  • Don't use misleading subject lines
  • Identify marketing emails clearly
  • Have permission to email recipients

Next Steps