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Optimizing Deliverability and Inbox Placement

Last updated February 2020

In order to get the best deliverability and inbox placement rates, you need to establish yourself as a legitimate sender by developing a good reputation with mailbox providers (like Gmail and Hotmail). Here’s how:

  1. Permission - only email to the people who have subscribed to receive your mail
  2. Transparency - make sure your content is relevant to the recipient. Display meaningful information in the Subject, From, and Reply-to headers
  3. Remove hard bounces (invalid recipient addresses) immediately from all future mailings
  4. Stop sending to recipients who don't want your mail, specifically: 
    • Remove spam complaints and unsubscribe requests
    • Remove inactive users (no opens/clicks in 30 days)
    • See below for more instructions on List Hygiene​
  5. Suppress recipients who you know (for any reason) should not be mailed to
    • If you are coming to SparkPost from Mandrill (or other provider) be sure to migrate your existing suppression lists (recipients who should not be mailed to) to via the Suppression List API.
  6. Ensure that DKIM is set up and verified for your sending domains
  7. Avoid the following BAD practices:
    • Sending messages without testing and proofreading
    • Hide the sender or use a misleading subject line
    • Hide the unsubscribe link or ignore unsubscribe requests
    • Buy email lists - especially those from untrustworthy sources
    • Sell your list to a third party without permission
  8. Set up custom bounce domain(s)
  9. Set up custom tracking domain(s)

For more detailed information on this topic, please review MAAWG Sender Best Common Practices.

List Hygiene: A Note On Event Types

You can find the following data using the Message Events API or raw event data streamed via webhooks.

Invalid Addresses

  • "Bounce" events indicate an invalid recipient, remove those with "bounce_class" = 10, 30, or 90 
  • "Out of Band" events that indicate an invalid recipient, remove those with "bounce_class" = 10, 30, or 90

Spam Complaints

  • "Spam Complaint" events


  • "List Unsubscribe" events
  • "Link Unsubscribe" events 

Note: If you aren't using our Link Unsubscribe feature, then you only need to register for "List Unsubscribe"

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