--- title: "Preview an Inbox Rule Without Sending Anything" url: https://www.insulin.dev/blog/preview-an-inbox-rule/ canonical: https://www.insulin.dev/blog/preview-an-inbox-rule/ type: Blog description: "Test an AI email rule without sending anything: what each of Preview's four steps checks, what one sample can't prove, and why a live rule goes quiet." --- # Preview an Inbox Rule Without Sending Anything > Canonical HTML version: https://www.insulin.dev/blog/preview-an-inbox-rule/ 1. [Home](/) 2. / 3. [Blog](/blog/) 4. / 5. Preview an Inbox Rule Without Sending Anything # Preview an Inbox Rule Without Sending Anything Test an AI email rule without sending anything: what each of Preview's four steps checks, what one sample can't prove, and why a live rule goes quiet. ![Max Ma](/authors/max-ma.jpg) Max Ma Sep 28, 2026 ![Preview an Inbox Rule Without Sending Anything](/images/blog/preview-an-inbox-rule/hero.png) Explore AI Summary [![](/logos/company/openai.svg)](https://chat.openai.com/?q=Read%20and%20summarize%20https%3A%2F%2Fwww.insulin.dev%2Fblog%2Fpreview-an-inbox-rule%2F%2C%20then%20cite%20the%20source.%20Focus%20on%20what%20it%20says%20about%20Inbox%20App%2C%20Automation. "Summarize with ChatGPT")[![](/logos/company/anthropic.svg) ](https://claude.ai/new?q=Read%20and%20summarize%20https%3A%2F%2Fwww.insulin.dev%2Fblog%2Fpreview-an-inbox-rule%2F%2C%20then%20cite%20the%20source.%20Focus%20on%20what%20it%20says%20about%20Inbox%20App%2C%20Automation. 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"Summarize with Perplexity") Table of Contents - [What does Preview do?](#what-does-preview-do) - [What does Preview never do?](#what-does-preview-never-do) - [Which prerequisites does the Check step look for?](#which-prerequisites-does-the-check-step-look-for) - [What can one sample not tell you?](#what-can-one-sample-not-tell-you) - [Why is a live rule not drafting?](#why-is-a-live-rule-not-drafting) - [Frequently asked questions](#frequently-asked-questions) - [Takeaways](#takeaways) _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._ * * * 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](/blog/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](https://doc.fours.com/insulin/inbox/#when-an-auto-send-rule-may-send). ## 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](/blog/email-rules-without-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](/inbox-app/). ## Sources Primary sources for the platform rules cited above. Last verified September 28, 2026. Cloud providers change fees, eligibility, and program terms without notice — check the source before relying on a figure. - [Insulin Inbox — Fours Doc](https://doc.fours.com/insulin/inbox/) — Preview's place between Details and Save, enabled exactly when Save is, running the rule as just written; its Interpret, Check, Sample and Run steps; that 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; the Preview only - not sent badge; the read-only sample labelled as a real record, a template or written by AI; Hide and editing behaviour; Save's five prerequisite checks and the user-level note; Save and Preview refusing an auto-send rule without one exact condition, and older auto-send rules shown as Skipped in the Rules (N of M fired) list; Inbox shipping no rules; Disable; CRM trigger Disable leaving rules dormant; the no-model state in which Inbox looks quiet; three Gmail attempts and the Failed badge; label-only rules; Details; the Approvals rule filter ## Keep reading - [Inbox AppAI Email Rule Templates: Exact Text, Word for WordOct 8, 2026](/blog/ai-email-rule-templates/) - [Inbox AppAuto-Draft a Follow-Up When a Deal Stage ChangesAug 18, 2026](/blog/crm-trigger-draft-reply-and-offer/) - [Inbox AppSetting Up Email Rules Without Writing CodeAug 16, 2026](/blog/email-rules-without-code/) - [Inbox AppHow AI Learns to Write in Your Own VoiceAug 14, 2026](/blog/ai-that-writes-in-your-voice/) [Browse every post on the Insulin Blog](/blog/) ### Stay Updated New posts, product updates and marketplace strategy are shared on LinkedIn as they publish. 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