Your system side

• List hygiene
  • Responding instantly to unsubs
  • Optin confirmation strategy
  • Removing or suppressing the unengaged
  • Removing hard bounces immediately
  • Removing soft bounces after the 3rd bounce • Master suppression list
• Engagement monitoring
• DKIM and SPF
• Properly formatted HTML
• Careful wording selection (spam assassin)
• Equal image to text ratio
• Monitoring abuse@ and postmaster@ addresses
• Volume and consistency
• Obey the law (can spam act)

Off your system factors
- Blacklists
- Accreditation programs
- ISP feedback loops
- ISP whitelisting