An Inbox rule is a small structured workflow: a trigger, a natural-language filter that decides which messages it applies to, the context it may draw on, and where the result goes. You write the filter as a sentence, not as a query language.
Traditional mail rules fail at exactly the point they become useful. They match on sender, subject and header — mechanical properties — so the moment you want “emails where a customer sounds unhappy about the renewal,” you are back to reading everything yourself.
Insulin rules match on meaning instead, which changes what is worth automating. The setup is four decisions, and the fourth is the one to think hardest about.
What is an Inbox rule?
A rule is a structured workflow with four parts: a trigger, a filter, context sources, and destinations.
| Part | What it is |
|---|---|
| Trigger | Email — the only option currently |
| Filter | A natural-language condition deciding which messages match |
| Context sources | Connected integrations the reply may draw on |
| Destinations | Where the outcome goes: Approvals, auto-send, or Slack |
Everything is configuration. There is no code, and the filter — the part that would be a query in any other tool — is a sentence.
Writing a filter that behaves
The filter is a natural-language condition, so the craft is in being specific about the situation rather than the words.
Describe the circumstance, not the vocabulary. “A customer asking when their contract renews” holds up. “Contains the word renewal” catches every newsletter that mentions one.
Say what should not match. Filters are easier to get right when they carry an exclusion. “A customer asking about pricing, not a vendor pitching us” removes the largest category of false positive in one clause.
Start narrow and widen. A rule that fires on too little is a rule you notice and fix. A rule that fires on too much trains people to ignore the queue it feeds, and that habit is hard to reverse.
Test on real mail before pointing it anywhere. Send it to Approvals first, watch what it catches for a few days, then decide what it should do.
Context sources: what the reply is allowed to know
Context sources are the connected integrations a rule may use while composing. This is what separates a useful draft from a polite one — a reply that can see the customer’s actual state says something worth sending.
Attach what the answer genuinely needs and nothing else. A rule that drafts replies about billing needs billing context. It does not need the whole workspace, and every extra source is a wider surface for something inappropriate to end up in a draft.
If the answers should come from your own written material rather than a live system, that is a knowledge base rather than an integration — and it brings citations with it, so you can check where a claim came from. Why AI answers need citations covers why that matters here specifically.
Destinations: the decision that actually matters
A rule’s outcome can go to the Approvals queue, be sent automatically, or notify Slack.
The default is Approvals, and it should stay the default. Insulin never sends email on its own — every AI-generated reply waits for human review, and sending requires a separate confirmation because it cannot be undone. Auto-send exists only for rules a person has explicitly authorised to skip that step.
Reserve auto-send for outcomes where being wrong is cheap and reversible: an acknowledgement, a routing notification, an internal ping. Anything that quotes a price, commits to a date, or is the first thing a customer hears from you belongs in the queue.
Slack notification is the underused third option. It tells a human that something arrived without drafting anything at all, which is exactly right for the category of mail that needs attention rather than an answer.
When the Inbox App acts and when it asks works through where that line belongs.
What connects today
Gmail is the supported email provider. The documentation notes Outlook was planned but not available as of July 2026, and cannot be connected — worth knowing before you plan a rollout around it. Check the changelog for the current position rather than assuming.
A rule worth building first
Pick the category of mail you personally handle most often, that has a predictable answer, and where being wrong is embarrassing rather than expensive.
Write the filter as a situation. Attach the one context source the answer needs. Send it to Approvals. Leave it for a week and read what it produced — not to approve it, just to see whether it caught the right mail.
That week tells you more about whether this works for your inbox than any amount of configuring will.
Frequently asked questions
Do I need to write code to set up a rule? No. A rule is configuration: a trigger, a natural-language filter, the context sources it may use, and a destination. The filter is written as a sentence.
What can a filter match on? Natural-language conditions about the message, so you can describe a situation rather than matching keywords or headers.
Which email providers work? Gmail. Microsoft Outlook was planned but not available as of July 2026 and cannot currently be connected.
Does a rule send email automatically? Only if you explicitly authorise it. By default drafts go to the Approvals queue, and Insulin never sends email on its own.
What are context sources for? They are the connected integrations a rule may draw on while composing a reply, so a draft can reflect the customer’s actual state rather than being generically polite.
Can a rule just notify someone? Yes. A destination can be a Slack notification, which suits mail that needs a human’s attention rather than a drafted answer.
Takeaways
- A rule is four decisions — trigger, filter, context, destination — and none of them is code.
- Write the filter as a situation, not as vocabulary, and include what should not match.
- Start narrow. A rule that over-fires trains people to ignore the queue it feeds.
- Attach only the context the answer needs. Every extra source widens what can appear in a draft.
- Keep Approvals as the destination. Auto-send is for outcomes that are cheap to get wrong.
- Slack notification is the right destination for mail that needs attention rather than an answer.
Most inboxes have one category worth automating first. See how the Inbox App classifies, drafts and queues it for review.
Sources
Primary sources for the platform rules cited above. Last verified August 16, 2026. Cloud providers change fees, eligibility, and program terms without notice — check the source before relying on a figure.
- Suger Insulin docs: Inbox — The rule structure of trigger, filter, context sources and destinations; that filters are natural-language conditions; that Gmail is the only supported provider and Outlook was not available as of July 2026; and the Approvals queue and auto-send destinations
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