The AI Email Assistant for Outlook vs Gmail

Most of Insulin’s Inbox app behaves identically on Outlook and Gmail — the rules, the triggers, Approvals, Send-and-confirm, the auto-send limits. Three things do differ, and the documentation states them plainly: attachments, where an AI draft lives, and whether you can edit and send a mailbox draft from Mails ▸ Drafts. This is the list an IT lead at a Microsoft 365 company needs before an Outlook team connects.

Updated October 8, 2026: the Inbox documentation now records a third provider difference — editing and sending a draft from Mails ▸ Drafts is Gmail-only — and says Gmail draft copies, labels and stars need the Gmail connection to carry Gmail’s gmail.modify permission. This post now covers both; earlier versions listed two differences and described the Gmail mirroring as unconditional.

---

If your company runs on Microsoft 365, the question before adopting an AI email assistant is narrower than “is it any good.” It is “does the Outlook version do what the Gmail demo did.” Insulin’s Inbox app connects to either provider, and for almost everything it does — reading a rule you wrote in plain English, staging a CRM action, holding a reply in Approvals until you press Send — the documentation draws no line between the two. Where it does draw one, it is worth knowing exactly, because one of the differences will refuse a send rather than degrade it quietly.

A note on how this post is written: it reports only what the Insulin Inbox documentation states for each provider. Where the docs describe a behaviour for Gmail and say nothing about Outlook, this post says so — it does not assume Outlook works the same way, and it does not assume it doesn’t.

Is the AI email assistant the same on Outlook and Gmail?

The Insulin Inbox app is one feature with one workflow on both providers, and the documentation records three provider differences: attachment support, where AI drafts are kept, and whether you can edit and send a mailbox draft from Mails ▸ Drafts. The core workflow it documents — the rule editor, CRM and marketplace triggers, the Approvals queue, the two-step Send-and-confirm, and the limits on auto-send rules — is described without reference to Gmail or Outlook. For an Outlook evaluator that is the headline: the automation you are buying is the automation the Gmail user gets.

The documentation does not say why each difference exists, and the Outlook message in Mails ▸ Drafts ends in “yet” — so read the list as today’s behaviour to re-check before a rollout, not as a fixed property of either mailbox.

Capability	Gmail	Outlook
Rules written in plain English	Yes	Yes
CRM & marketplace triggers	Yes	Yes
Approvals queue, Send and confirm	Yes	Yes
Auto-send rules (one exact condition)	Yes	Yes
Attachments	Up to 3 files × 5 MB, both directions	Not supported, either direction
Where AI drafts live	In Approvals, and mirrored into the Gmail Drafts folder when the connection carries gmail.modify	In Approvals only — not mirrored to Outlook
Edit and send drafts in Mails ▸ Drafts	Yes — Save writes back to Gmail; Send asks you to Confirm send	No — the view reads “Live drafts aren’t available for this mailbox provider yet.”
Label sync to the mailbox	Real Gmail labels, when the connection carries gmail.modify (documented)	The documentation describes this for Gmail
Retry on provider errors	Three attempts, then a Failed badge (documented)	The documentation describes this for Gmail

The last two rows are the careful ones, and the next sections explain why they are phrased the way they are.

What is different about attachments on Outlook?

On Outlook, attachments are not supported in either direction; on Gmail they are, up to 3 files of 5 MB each. The documentation’s Attachments section states that Gmail handles attachments normally both ways, including files forwarded from the original message. Outlook has none of that, and the consequences are specific:

• Incoming Outlook messages show no attachment list in Inbox. A file a sender attached is simply not surfaced.
• An Outlook send that carries attachments is refused with an error — rather than silently going out without them. This is the difference that matters most in practice: the assistant will not quietly drop a file and send an incomplete message. It stops and tells you.
• The Attach control is not shown on an Outlook mailbox. There is no affordance to add a file in the first place, which is consistent with a send that would be refused anyway.

For most reply automation this is a non-issue — a drafted reply is text. It becomes a real constraint the moment a workflow expects to send a file: a contract, a report, an invoice. On Outlook, that is not an Inbox-app path. If your Outlook team’s email work routinely ships attachments, route those messages through Outlook itself and let Insulin handle the drafting and the CRM side.

Where do AI drafts show up on Outlook?

On Outlook, an AI draft lives in Insulin’s Approvals queue and is not mirrored into your Outlook mailbox; on Gmail, each AI draft is also mirrored into the native Gmail Drafts folder, provided the Gmail connection carries Gmail’s gmail.modify permission. For a Gmail user the documented behaviour is a full lifecycle: Insulin creates the Gmail draft when the reply is generated, updates it when you edit, and deletes it when you send or archive from Inbox. An Outlook user gets the same review experience inside Insulin — the draft is in Approvals, ready to read, edit, send or discard — but nothing appears in Outlook’s own Drafts folder.

The Gmail condition covers more than drafts: the draft copies and the labels and stars Inbox mirrors to Gmail all need gmail.modify. Without it nothing is copied to Gmail, but Inbox itself works as before — drafts still wait in Approvals ▸ Pending, and labels and stars still show in Inbox. Enabling Inbox runs its own check: if a Gmail connection was authorized without a permission Fours’ Gmail connection now asks for, Enable Inbox for Gmail under Settings → Account fails with Gmail health check failed and names the missing permission. Disconnect and reconnect Gmail in Settings → Integrations, then try again.

The practical effect is about where an Outlook reviewer looks. If part of your team expects to open Outlook and find AI drafts waiting there, set the expectation early: on Outlook, Approvals is the drafts folder. For the full picture of what Insulin stores while a mailbox is connected — on either provider — see what an AI email assistant keeps about your email, which walks the retained-data inventory row by row.

Can you edit and send drafts from Mails on Outlook?

No — editing and sending a draft from Inbox’s Mails ▸ Drafts view is Gmail-only; on an Outlook mailbox, that view reads “Live drafts aren’t available for this mailbox provider yet.” AI drafts are not affected: on either provider they wait in Approvals ▸ Pending, where you edit one, press Send and confirm. What an Outlook mailbox lacks is a second place to finish a draft.

On a Gmail mailbox, Mails ▸ Drafts lists the drafts in your Gmail Drafts folder — your own, and the ones Inbox mirrored there — and opens one in a composer. You edit To, Cc, Subject and the body; Save writes your edits back to the draft in Gmail; Send asks you to Confirm send — “This sends from your mailbox immediately.” — then sends the draft, saving your edits first so what goes out is what is on screen; and Open in Gmail opens the same draft in Gmail. Sending a draft Inbox mirrored from Approvals ▸ Pending completes that approval: it leaves Pending and is recorded in History as a sent email.

Four Gmail cases behave differently, and each says so on screen: a draft with attachments can only be sent exactly as saved; a draft that changed in Gmail after you opened it is not sent, and Reload draft loads the latest version; sending a leftover copy of an email Approvals already sent is refused; and without permission to change drafts, Save and Send show a message instead, telling you to reconnect Gmail or to open the draft in Gmail.

For an Outlook team the working rule is simple: AI drafts are finished in Approvals ▸ Pending, and drafts started in Outlook are finished in Outlook, not in Inbox.

Are rules, triggers, and Approvals different on Outlook?

No — the documentation states no provider difference for rules, CRM and marketplace triggers, the Approvals queue, Send-and-confirm, or the auto-send limits. A rule you write in plain English is interpreted, checked and run the same way; a CRM action stages the same way; a reply waits for the same explicit Send-and-confirm before anything leaves your mailbox. The one exact-condition requirement that governs an auto-send rule is provider-neutral too.

That means the muscle memory transfers. If your team has read how to preview an Inbox rule without sending anything, the four Preview steps — Interpret, Check, Sample, Run — behave identically for an Outlook mailbox. The Check step’s prerequisites include an enabled mailbox, and the only provider-specific thing there is which button you clicked: Enable Inbox for Outlook rather than Enable Inbox for Gmail.

Two documented behaviours are described in Gmail’s terms and the documentation is silent on Outlook, so this post will not claim they apply to Outlook or that they don’t:

• Label sync. The documentation describes labels syncing to the mailbox as real Gmail labels on a Gmail connection that carries gmail.modify; without it, nothing is copied to Gmail, though labels and stars still show in Inbox. It does not describe label sync for Outlook, so treat Outlook label behaviour as unstated rather than assume parity.
• The three-attempt retry and the Failed badge. The documentation describes Inbox retrying a message across three attempts when Gmail is briefly unavailable or rate-limits it, then marking the message Failed. It describes this for Gmail; it does not state the equivalent for Outlook.

If either of those matters to your rollout, confirm the current Outlook behaviour with Fours rather than reading it off the Gmail description.

One mailbox at a time: what an Outlook switch deletes

Only one email provider can be the Inbox mailbox at a time, and switching from one to the other permanently deletes the old provider’s stored mail. This is the paragraph to read before anyone on the team “just tries” Outlook on a mailbox that was already running Gmail. Per the documentation, switching permanently deletes the old provider’s emails — including AI-applied categories, drafts, and classification history. Your writing-style profile is rebuilt from the new mailbox.

Because it is destructive, the switch is gated: you must type the literal word SWITCH into the confirmation box, and the button stays disabled until it matches. That confirmation is the tell that this is not a casual toggle. The mailbox lifecycle actions — Disable, which keeps your processed mail, and the destructive Disconnect and Switch — are covered in what Disable and Disconnect do to your mail.

Before an Outlook team connects: a short checklist

Run this before you enable Inbox for the first Outlook mailbox at your Microsoft 365 company:

1. Confirm attachments aren’t on the critical path. If a workflow needs to send files, know that an Outlook send carrying attachments is refused — route those through Outlook directly.
2. Set expectations on drafts. On Outlook, AI drafts stay in Approvals, not the Outlook Drafts folder, and Inbox’s Mails ▸ Drafts view does not open Outlook drafts. Tell reviewers to finish drafts in Approvals ▸ Pending.
3. Decide the provider once. Only one mailbox connects at a time, and switching later permanently deletes the first provider’s stored mail; the confirmation makes you type SWITCH.
4. Connect the integration, then enable. Set up the Outlook integration under Settings, then click Enable Inbox for Outlook — Inbox reuses that connection rather than running its own sign-in.
5. Verify the unstated bits directly. If label sync or retry behaviour is load-bearing for you, confirm the Outlook specifics with Fours, since the documentation states them for Gmail.
6. Start on Draft for review. Keep new rules drafting for review — for example, a rule that watches messages from [email protected] — and read what they catch before trusting an auto-send rule.

Frequently asked questions

Does the AI email assistant work with Outlook?

Yes. Insulin’s Inbox app connects to Outlook or Gmail, and the documentation describes the same rules, CRM triggers, Approvals queue and Send-and-confirm flow on both. The three documented differences are attachments, where AI drafts are kept, and editing drafts in Mails ▸ Drafts, which is Gmail-only.

Can Insulin send attachments from Outlook?

No. The documentation states attachments are unsupported on Outlook in both directions. Incoming messages show no attachment list, the Attach control is not shown, and an Outlook send that carries attachments is refused with an error rather than sent without them.

Where do AI drafts appear for an Outlook mailbox?

In Insulin’s Approvals queue, not the Outlook Drafts folder, and on Outlook the Mails ▸ Drafts view reads “Live drafts aren’t available for this mailbox provider yet.” On Gmail, AI drafts are also mirrored to Gmail Drafts when the connection carries the gmail.modify permission.

Are Inbox rules different on Outlook than on Gmail?

No. The documentation records no provider difference for rules, CRM and marketplace triggers, Approvals, Send-and-confirm, or the auto-send limits. A plain-English rule is interpreted and run the same way on either provider.

Does Insulin sync labels on Outlook?

The documentation describes labels syncing as real Gmail labels when the Gmail connection carries the gmail.modify permission, and does not state the equivalent for Outlook. Treat Outlook label behaviour as unstated rather than assume it matches Gmail, and confirm with Fours if it matters to your rollout.

Can I connect both Gmail and Outlook at once?

No. Only one provider can be the Inbox mailbox at a time. Switching to the other permanently deletes the old provider’s stored emails, AI categories, drafts and classification history, and makes you type the word SWITCH to confirm.

Takeaways

• The Inbox app is one workflow on both providers; the documentation records three provider differences — attachments, where AI drafts are kept, and editing drafts in Mails ▸ Drafts.
• Attachments: Gmail allows up to 3 files of 5 MB in both directions; Outlook supports none, and an Outlook send carrying attachments is refused with an error.
• Drafts: on Outlook, AI drafts stay in Approvals, are not mirrored, and Mails ▸ Drafts reads “Live drafts aren’t available for this mailbox provider yet.” On Gmail, AI drafts are also mirrored into the Gmail Drafts folder when the connection carries gmail.modify, and Mails ▸ Drafts can edit a Gmail draft and send it after Confirm send.
• Label sync (on a Gmail connection with gmail.modify) and the three-attempt retry plus Failed badge are documented for Gmail; the documentation is silent on Outlook, so verify those directly.
• One mailbox at a time — switching permanently deletes the old provider’s stored mail and makes you type SWITCH.

Ready to see the review-first workflow that is the same on either provider? Explore how the Inbox app drafts replies and stages CRM actions for your approval.