Review quarantined mail

MachineMail quarantines a message when its trust report finds it dangerous: it looks like phishing, carries instructions aimed at an AI agent, or carries a virus. A quarantined thread gets the QUARANTINE label instead of INBOX. Agents do not see it unless they ask for quarantined mail on purpose.

Mail from a sender on a block list is handled differently. It gets the BLOCKED label instead, and agents don’t see it either.

A person decides what happens next. This guide shows how to do that in the dashboard. To handle quarantine in code, see Using trust in agents.

1. Find quarantined threads

   Open machinemail.dev/app/threads?label=QUARANTINE.

   Or go to Threads, open the Label filter and choose QUARANTINE. Add the Inbox filter to look at one inbox.

   Quarantined threads do not appear in an inbox’s own list or in the unfiltered Threads list. The label filter is how you find them.

2. Open the thread

   Select a thread. A red Quarantined banner sits at the top: “Agents don’t see this thread unless they list with include_quarantine. Review the trust report before releasing it.”

   You can’t reply to a quarantined thread. The reply box says Release the thread before replying.

3. Read the trust report

   Each message has a Trust report bar at the bottom, with the number of reasons. Click it to open the report. You can also right-click the message and choose View trust report. On a phone, use the ⋯ menu on the message.

   The report has these parts:

   Part	What it tells you
   Verdict	The score (higher is safer) and the level: Verified, Known, Unknown, Suspicious or Quarantined.
   Authentication	SPF, DKIM and DMARC results, and whether they line up with the From address.
   Sender	How often this inbox has written to and heard from the sender, and flags such as On block list or Free mail provider.
   Content scrub	What MachineMail removed before agents saw the text: hidden text, zero-width characters, tracking pixels.
   Classifier	How likely the message is to contain instructions to an agent, phishing, a request for credentials or payment, or spam.
   Reasons	The plain reasons behind the verdict. Start here.
   Links	Each link, with warnings such as a visible text that names a different domain than the real destination.
   Attachments	Each attachment with its risk and reasons.

   The trust report explains every field.

4. Compare Agent-safe and Raw

   The switch at the top right of the thread has two views:

   • Agent-safe shows the text an agent would read. Pieces MachineMail removed appear as chips under the text, for example Hidden text removed with its length.
   • Raw shows the original text, with hidden text highlighted in red, and the message’s headers.

   Hidden text that tells an agent what to do is the usual reason for a quarantine. Raw shows you exactly where it was.

   Right-click a message to copy the Agent-safe text or the Raw text, or to Download raw .eml.

5. Release or block

   Use the buttons on the Quarantined banner:

   • Release moves the thread back to the inbox. It shows up in message lists again, and you can reply. The trust report itself does not change: the level stays Quarantined, and the MCP tools keep withholding the content.
   • Block followed by the sender’s domain (for example Block example.com) adds the domain to your organization’s receive block list. Type DELETE and confirm. From then on, mail from that domain to any inbox is labelled BLOCKED and withheld from agents, until you remove the rule on Lists.

   Blocking does not release or delete the thread in front of you. To remove it too, right-click it in the thread list and choose Move to trash or Delete thread.

   If you do nothing, the thread stays quarantined and agents keep ignoring it.

Other things you can do

Right-click any thread in a list for more actions:

• Release from quarantine does the same as Release on the banner.
• Quarantine moves a thread that got through into quarantine, so agents stop seeing it.
• Block followed by the domain blocks the sender’s domain from the list. For a sender on your own domain, or one with no domain, the item reads Block sender domain and is greyed out.

Troubleshooting

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