Preview an Inbox Rule Without Sending Anything

Preview is the Inbox rule editor’s dry run. It runs the rule you are writing against one read-only sample event and shows what a live event would have produced, but it writes no approval row, sends no email, posts no Slack message, takes no CRM action and does not move the trigger’s stage cursor.

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Before you switch on an Inbox rule that drafts replies, messages you on Slack or queues CRM work, you want to see what it will do. Once it has run for a while, the question can turn around: why has it gone quiet?

Insulin’s rule editor answers the first with Preview, which is how you test an AI email rule without anyone receiving anything. The Inbox documentation answers the second with a short list of states to check. This post covers both, starting where writing an email rule in plain English stops: that post covers the editor itself, and why Save fails rather than write a rule that matches every email.

What does Preview do?

Preview runs the rule as you have just written it, not the version last saved, through four steps against one sample event. It sits between Details and Save, is enabled exactly when Save is, and narrates each step with how long it took and what it produced.

Step	What happens	What it can catch
Interpret	Turns your description into a structured rule: the same call Save makes	A description read as a different rule from the one you meant
Check	Compares what the rule needs with what you have connected. A rule missing a piece stops here	A missing model, mailbox, CRM trigger, Slack connection or context source, before the rule runs
Sample	Produces one sample event to run against: read-only, and labelled with where it came from	Nothing by itself. It tells you what the verdict rests on
Run	Does the real matching and drafting, and shows the verdict plus each output, labelled with what a live event would have done	A rule that doesn’t match the event you expected, a draft that reads wrong, or an output headed somewhere you didn’t intend

The Check step stops instead of working around a gap because, as the documentation puts it, a rule missing a piece “is not the rule you meant to test.” Two behaviours matter once results are on screen:

• Editing the description dismisses the results, because they belonged to the description they ran on.
• Hide only collapses the panel. Showing it again does not run the preview again.

What does Preview never do?

Nothing goes out and nothing is queued: a preview writes no approval row, sends no email, posts no Slack message, takes no CRM action, and does not move the trigger’s stage cursor. Every output card is badged Preview only - not sent, and each output stays on its card instead of going where a live event would send it.

Sending nothing is not the same as reading nothing. The sample is read-only and labelled with where it came from: a real record, a template, or written by AI, so a generated example is never mistaken for a real one. When the sample is a real record, Preview reads it and still acts on nothing. Its promise is about outbound actions, not about data it never sees.

Which prerequisites does the Check step look for?

Five: an AI model, an enabled mailbox, the CRM and its trigger when the rule uses one, Slack when the rule delivers there, and every context source the rule names. Save runs the same checks and refuses on the same grounds, so a rule that fails one in Preview is not saved either.

Check	Fails when	Fix
AI model	No model is available to interpret the description	Connect a model provider on the Integrations page. The AI model section of Settings → Account shows which are connected
Mailbox	No mailbox is connected, or one is connected but not enabled	Under Settings → Account → Email source, click Enable Inbox for Gmail or Enable Inbox for Outlook, connecting the mailbox under Integrations first if needed
CRM	The rule uses a CRM that is not connected, or is connected with its trigger disabled	Connect your own Salesforce, HubSpot or Microsoft Dynamics 365, then Enable its row under Settings → Account → Triggers
Slack	The rule delivers to Slack, and Slack is not connected	Connect your own Slack under Settings → Integrations → User Integrations
Context sources	A context source the rule names is missing or cannot be resolved	Connect it as a user integration, or take it out of the description

Every check is on your own, user-level connections. The fix links point at Settings → Integrations → User Integrations or your Account page, and connecting the same tool at the organization level does not satisfy them. If a check fails for something you are sure is connected, look at which level it is connected at.

One refusal belongs to auto-send alone: when a rule set to Send automatically has a description that doesn’t compile to one exact, narrowing condition, Save says Nothing was saved. and gives the reason, and Preview stops with the same reason. The documentation sets out the limits an auto-send rule has to meet.

What can one sample not tell you?

Whether the rule covers your mail: one sample is not proof of coverage. A preview shows how the rule behaves on one event, and that event may be a template or written by AI rather than anything you received. A match shows the rule can fire; it says nothing about the mail the sample doesn’t resemble.

Question	Does Preview answer it?	Where the answer is
Was my description read as the rule I meant?	Yes: Interpret shows what it produced	Once the rule is saved, Details shows its trigger, filter, context sources, generation inclusions and exclusions, and actions
Is everything the rule needs connected?	Yes, at the moment it runs	The table in the next section, if something changes later
Does it fire on the mail I meant, and on nothing else?	No: it ran on one event	The rule’s first live results, drafted for review
How often will it fire?	No	Approvals ▸ Pending, narrowed to that rule with the rule filter
Will the reply or the Slack message arrive?	No: nothing was sent or posted	The first live event
Is the live rule the one I previewed?	Not until Save succeeds, because Preview runs the unsaved description	Details, after you save

The habit that closes the gap is the one setting up email rules without writing code recommends: keep the rule on Draft for review and read what it catches for a few days. Nothing such a rule produces reaches anyone but you until you act. A reply waits for Send and a confirmation, a CRM action waits for you to click Run in chat, and a Slack notification is a DM to you.

Why is a live rule not drafting?

Check in order from the whole inbox down to one message: first what silences every rule, then what silences one rule, then what the mail itself shows. Before any of that, make sure a rule asks for a draft at all. Inbox ships no rules of its own, so nothing is drafted until one does.

What you see	Likely cause	Where to look	What to do
Inbox looks quiet: no rule drafts anything	No AI model is available: no provider of your own, and hosted models not allowed for your organization	The AI model section of Settings → Account	Connect a model provider. Preview names this as the first thing to fix
No new mail is being processed	The mailbox is connected but not enabled, or Inbox has been Disabled	The mailbox card under Settings → Account → Email source, which shows Inbox enabled once Inbox is running	Enable it. Mail already processed was kept
One rule stays silent	Its switch is off, or the CRM trigger it relies on is disabled, which leaves the rule saved but dormant	The rule’s row in Settings → Rules, or the trigger’s row under Settings → Account → Triggers	Switch the rule on, or Enable the trigger
An edit never took effect	Save refused it and wrote nothing, so whatever was saved before is what runs	The rows Save showed, each with its reason and a link to the fix	Fix each row and save again
The rule fires but never drafts	It has no Email reply action: a rule can label only, or only notify you on Slack	The Actions in the rule’s Details	Describe the reply you want, and save
One mail got nothing	The rule’s filter didn’t match that mail	The mail’s Rules (N of M fired) list, in the conversation view	Describe the situation more precisely, then preview the new wording
A Gmail message shows Failed	Gmail was unavailable or rate-limited Insulin through all three attempts	The conversation view	Reply to it yourself: it has no draft
An auto-send rule shows Skipped	It is an older auto-send rule, saved before Save began checking for one exact condition, and it never fires	The mail’s Rules (N of M fired) list, which gives the reason	Rewrite it around a specific sender, subject or body condition, or switch it to drafts

Frequently asked questions

Does Preview send anything?

No. A preview writes no approval row, sends no email, posts no Slack message, takes no CRM action and does not move the trigger’s stage cursor. Every output card is badged “Preview only - not sent”.

Does Preview read my real data?

It can. Preview runs on one read-only sample event and says where it came from: a real record, a template, or written by AI. It matches and drafts against that sample, but sends, posts and queues nothing.

Why did Preview stop at the Check step?

Something the rule needs is missing from your own, user-level connections: an AI model, an enabled mailbox, a CRM with its trigger enabled, Slack, or a context source the rule names. An organization-level connection doesn’t count, and Save refuses on the same grounds.

If a preview matches, will the rule catch my real mail?

Not necessarily. A preview runs on one sample, which may be a template or written by AI, so it shows how the rule behaves on that event alone. Keep the rule on Draft for review and read what it catches before you trust it further.

Why isn’t my live rule drafting anything?

Check that an AI model is available, the mailbox is enabled, the rule and any CRM trigger are switched on, and your last edit saved. Then open a mail the rule missed: look for a Failed badge, and read its Rules (N of M fired) list.

Why does my auto-send rule show Skipped?

It is an older auto-send rule, saved before Save began checking for one exact, narrowing condition, and it never fires. Rewrite it around a specific sender, subject or body condition, or switch it to drafts. Save and Preview both refuse an auto-send rule without one.

Takeaways

• Preview runs the rule as you have just written it through four steps (Interpret, Check, Sample, Run) against one read-only sample event.
• It writes no approval row, sends no email, posts no Slack message, takes no CRM action and does not move the trigger’s stage cursor.
• The sample may be a real record, a template or written by AI. One sample shows the rule can fire; it is not proof the rule covers your mail.
• The Check step looks at your own user-level connections, so an organization-level connection does not satisfy it.
• When a live rule goes quiet, work down from the model and the mailbox to the rule’s switch and trigger, then to the mail itself.

Preview shows you what a rule does with one event before it acts on any, and a rule that drafts for review shows you what it does with real mail before anyone else sees a word. See how the Inbox App turns a plain-English rule into replies you approve.