Inbox Placement

Inbox Placement is a tool which allows visibility into knowing where your email will land in the mailbox, I.e., inbox, spam/junk folder. While mailbox providers (Gmail, Yahoo, Hotmail, etc.) supply feedback to inform whether an email was delivered or not, they do not supply insight on where a message has landed. Mailgun's Inbox Placement uses a mechanism known as seed testing which supplies visibility into where emails land.

The seed testing process is as follows:

  1. Mailgun manages a list of seed mailbox accounts with each mailbox provider in the market.
  2. A test email is sent to the seed list.
  3. Mailgun tracks where the test email has landed for each mailbox in the seed list and returns the results to the user. The results have the following information:
  4. "Spam", "Missed", or "Inbox" placement (also which tab for Gmail mailboxes) for each individual mailbox in Mailgun's seed list.
  5. A rollup percentage summary for each mailbox provider. The rollup aggregates the results from the mailbox.
  6. A rollup percentage summary for each seed test. The rollup aggregates the results from each mailbox provider.

For more information about Inbox Placement, visit the Inbox Placement FAQ.

Creating a Test

Creating and running an Inbox Placement test is simple and requires minimal configuration in either the control panel or the API with the following requirements:

  • A sending domain to send a test from. If you haven't set up a domain, please see [Verifying Your Domain.](# Verifying Your_Domain)
  • A message subject
  • A message body


  • Provide a 'from' address prefix. Mailgun provides a 'user' by default.

Once configured, a test can be performed.

Test Results

When an Inbox Placement test is performed, Mailgun will try to match (or group) all the emails sent to the various seed mailboxes together to test a result. This is done by using email criteria, such as sender, timeframe, headers, and subject.


To ensure accurate test results and reduce missing email rates, Mailgun recommends setting a unique "matching" header per test. See the example below.

[Code sample of an Inbox Placement test result]

Below is a list of supported (case insensitive) email headers that will be used to match emails when generating Inbox Placement test results:

  • X-IBP-DebugHeader
  • X-Mailjet-Campaign
  • X-job
  • X-cid
  • X-NSS
  • X-250ok-CID
  • X-rpcampaign
  • rpcampaign
  • X-PVIQ
  • X-Campaign-ID
  • X-CampaignID
  • X-10pl8ID
  • X-Campaign _ ID
  • X-eC-messenger-mid
  • X-EMarSys-Identify
  • X-jobid
  • X-Listid
  • X-MailingID