Fixing Emails Sent from Microsoft 365 Email Going to Spam

Potential Issues Causing Emails Going to Spam Folder:

  • Missing Unsubscribe Link
  • Content has different HTML Versions and/or broken HTML
  • Email size over 100kb
  • Domain Reputation is Poor
  • Inconsistent Email Volume
  • IP Reputation is Bad: IP Server not configured properly, Not having TLS Authentication, IP not having Return Path Certificate, Not having an inbox for a “from email” OR “reply-to” email address that is used while sending the email over the IP
  • Email Authentication Is Failing in 3rd party ESP
  • Configured DKIM and DMARC. Email systems that receive email from your domain can use this digital signature to help determine if incoming email that they receive is legitimate. 
  • Email Engagement Is Poor: Majority of your users don’t open your email, Malformed From Email address

Suggestion from Microsoft Docs Service:

“If SPF records for your domains are properly configured and your IPs/domains aren’t blacklisted, the best approach would be asking the recipient domain’s email admins to perform a message trace at their end.”


  • Determine if emails are entering the spam folder of all recipients or specific recipients. If it is certain recipients then you can try contact them to tell them to add your sending IP addresses/email address or domain to their allowed/safe senders list to see whether the problem still occurs.