Email Deliverability Guide
Practices for Successful Email Sending

A summary of key email deliverability practices for ensuring your messages reach inboxes.

👋 New to Mailtrap? Check our 5 minute 🎥 overview of our Email API/SMTP.

Highlights: The golden rules of email deliverability

Send expected content at expected times

  • Only send emails recipients explicitly signed up for
  • Maintain consistent sending schedules
  • Match content to subscriber expectations

Less is more

  • Focus on engaged subscribers
  • Remove inactive subscribers
  • Prioritize email list quality of over email list size

No cold outreach

  • Avoid cold email campaigns, as they are considered SPAM
  • Follow Mailtrap’s guidelines, which prohibit cold outreach
  • Only send to verified opted-in subscribers

Protect all web forms

  • Implement CAPTCHA on every form
  • Prevent bot-generated sign-ups
  • Validate web form entries 

Following these key guidelines will help you prevent common deliverability issues. For in-depth guidance, explore the rest of this page.

Foundation: Technical setup

Domain authentication:

  • Configure SPF and DMARC records correctly, ensuring there are no conflicting entries. With Mailtrap, this is already covered.
  • Set up proper A and MX records for your domain (via Cloudflare, Google Workspace, or other services).
  • Consider using separate subdomains for marketing and transactional emails (e.g., email.yourdomain.com for marketing, notifications.yourdomain.com for transactional)
  • Verify domain ownership through Google Postmaster Tools for enhanced deliverability monitoring. 

Tip: Provide view access to your Google Postmaster Tools dashboard to Mailtrap’s support team for additional deliverability monitoring (applies to Business and higher plans).

Form security:

  • Implement CAPTCHA protection on all forms:
    • Newsletter subscription forms
    • User registration forms
    • Contact forms
    • Password reset forms
  • Use trusted CAPTCHA solutions:
  • Consider additional security measures:
    • Implement honeypot fields (invisible fields designed to remain empty and trap bots)
    • Add timing checks (a measure to block submissions completed in under 1 second)
    • Limit requests by IP address

Email list management

  • Clean your lists by removing:
    • Role-based emails (admin@, info@, sales@, support@)
    • Disposable email domains
    • Misspelled email domains (example@gmal.com)
    • Invalid email addresses
  • Use email validation services before sending campaigns:
  • Implement a sunset policy for your lists:
    • Define inactivity thresholds (e.g., no opens for 6 months)
  • Send re-engagement campaigns
  • Remove consistently inactive subscribers

Sender identity shaping

  • Use engaging sender addresses:
    • Instead of “no-reply@company.com” try “newsletter@company.com”, “updates@company.com”, “team@company.com”
  • Format “From” names professionally:
    • Use names like “John from Company” john@company.com and “Company Newsletter” newsletter@company.com
    • Avoid (if possible) “DO NOT REPLY” no-reply@company.com
  • Monitor reply addresses:
    • Set up auto-responses for marketing emails
    • Route subscriber replies to the support team
    • Track reply engagement for deliverability metrics

Content creation

Message structure

  • Subject line:
    • Include company name for recognition
    • Keep the length under 50 characters
    • Use formats like “Your Company: November Product Updates”
    • Avoid spam trigger words like “AMAZING OFFER!!! DON’T MISS OUT!!!”
  • Pre-header text (preview text):
    • Keep the length at: 40-130 characters
    • Use text to complement the subject line
    • Use formats like “See what’s new in our latest release, including highly-requested features”
  • Email copy:
    • ​​Keep paragraphs short and scannable
    • Focus (if possible) on one key message per email
    • Include a clear and compelling call-to-action (CTA)
    • Avoid spam trigger words and excessive punctuation
    • Optimize for mobile readability

Email sending

Gradual scaling

Build your sending reputation carefully:

  • Start with 200 emails per day and gradually increase every day and week
  • Focus on your most engaged subscribers (those who have interacted with your emails in the last 30 days)
  • Increase volume by 25-30% every few days
  • Monitor bounce rates (ensure they stay below 2%)

Note: If you have questions, the Mailtrap deliverability team is ready to help. Assistance is included in the Business and higher plans.

Engagement-based communication

  • Segment your lists based on engagement levels:
    • Highly engaged (opened/clicked in last 30 days)
    • Somewhat engaged (opened/clicked in last 90 days)
    • At risk (no opens/clicks in 90-180 days)
    • Inactive (no opens/clicks in 180+ days)

Tip: Avoid sending any communication to the Inactive segment if your case allows it.

  • Implement double opt-ins:
    • Follow up the opt-in with an immediate confirmation email
    • Include clear confirmation instructions within the email
    • Set an expiration timeframe for any confirmation links (24-48 hours recommended)
  • Enable easy unsubscribing:
    • Include a one-click unsubscribe option in every email
    • Link to the preference center for frequency adjustment
    • Provide a clear unsubscribe confirmation message

Prohibited Practices

Maintain good standing with Mailtrap:

  • Don’t send cold outreach campaigns
  • Don’t use purchased or rented email lists
  • Don’t write deceptive subject lines or content
  • Don’t attempt to bypass spam filters through content manipulation

Maintenance: Monitoring and audits

  • Use Google Postmaster Tools:
    1. Visit Google Postmaster Tools
    2. Add and verify your domain
    3. Get insight on:
      • Spam rate
      • Domain reputation
      • IP reputation
      • Delivery errors
      • Authentication results
  • Monitor key metrics:
    • Bounce rate (keep under 5%)
    • Spam complaints (keep under 0.1%)
    • Open rates (industry average 15-25% for bulk emails)
    • Click-through rates (industry average 2.5% for bulk emails)
  • Verify SPF, DKIM, and DMARC authentication settings
  • Test email formatting across different clients and devices
  • Ensure compliance with Google email sender guidelines
  • Ensure compliance with CAN-SPAM, GDPR, and other regulations

Tip: View email deliverability as an ongoing process that requires regular attention and adjustment. Keep testing, monitoring, and optimizing based on your metrics and recipient engagement.

Useful Mailtrap information

Additional resources

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