Why does my Everest inbox test show missing mail at a B2B filtering company?

Troubleshooting B2B deliverability can be a challenge. Many companies deploy third-party spam filters (e.g. Mimecast) in addition to their email client (e.g. Microsoft Office 365) to protect their users from spam and phishing attacks. Because these filters add an extra layer of protection, they can influence inbox placement tests separately from mailbox providers.

Without a filtering company

In the standard setup, a sender's email goes directly to the mailbox provider. The mailbox provider decides whether that email passes its gateway or gets blocked. Blocked mail shows up as missing in inbox provider tests. After that, the mailbox provider decides whether email that gets past the gateway goes directly to the inbox or gets held in the spam folder.

Flow summary:

• Sender to mailbox provider gateway
  • Blocked at gateway: missing
  • Passes gateway: goes to mailbox provider filtering
• Mailbox provider filtering
  • Inbox
  • Spam

With a filtering company

But when a business uses a filtering company for its mail, a sender's email first goes to that filtering company, before it ever goes to the mailbox provider. (In many such cases, the MX record for the business domain points to the filtering company, not the mailbox provider.) 

The filtering company decides whether to block mail entirely, hold it in quarantine, or pass it on to the mailbox provider. These decisions can be configured by IT administrators, so one company may choose to block all suspicious mail, while another may choose to pass all suspicious mail to quarantine, and a third may use a mix of options.

Quarantined mail, also called held mail, functions as a sort of spam folder at the filtering company level.

• The filtering company may send an email to the mailbox provider with a list of quarantined or held mail, with options for releasing or blocking each item.
• Otherwise, quarantined mail stays with the filtering company until the recipient signs in to review and release messages.

Released mail then is passed to the mailbox provider.

Note: Quarantined mail that has been released generally does not go to the mailbox provider's spam folder, but straight to the inbox.

Flow summary:

• Sender to filtering company
  • Blocked at filtering company: missing
  • Quarantined at filtering company: missing until released
  • Passes filtering: goes to mailbox provider gateway
• Filtering company to mailbox provider gateway
  • Blocked at gateway: missing
  • Passes gateway: goes to mailbox provider filtering
• Mailbox provider filtering
  • Inbox
  • Spam

Why quarantined mail shows up as missing in Inbox Placement

If messages sent to the Everest Seed List end up in quarantine at a filtering company, Everest is not alerted that those messages are being held. Everest simply sees that those messages have not arrived for a specific test at a specific address, and it shows them as missing in Inbox Placement.

Any quarantined mail that is released while Everest is still collecting test data will eventually move out of the missing column to the inbox (or, rarely, spam).

Which filtering companies can release to the spam folder?

In most cases, quarantined mail goes directly to the inbox when released. But according to Validity testing, some filtering companies can release mail to the spam folder instead of, or in addition to, the inbox in their default configurations.

Note: Individual businesses may have different results, depending on how their IT departments have configured the filtering company's settings.