Sintra's Cassie AI: Inbox Sorting, Draft Replies and Hard Limits

Cassie is Sintra's customer support helper, and she writes drafts, not replies. Through the Inbox Manager automation she sorts Gmail or Outlook mail into 8 fixed categories and drafts answers for three of them. Through Facebook Commenter she drafts replies to comments on a connected Facebook Page. Every reply waits for you ^[1]. She is not a chatbot. She cannot sit on your website, answer WhatsApp or reply to DMs on her own. Pick her for a faster first draft in a small business inbox; skip her if answers must go out while you sleep.

Cassie is not sold alone. She comes inside Sintra X, the single plan with all 12 helpers, at $48.50 a month billed monthly or $15.60 a month billed yearly ($187.20 paid upfront for the year), with 250 credits a month. Sintra does not guarantee the renewal price: its Terms say renewals are charged at the then-current rate and offer prices may apply only to the first term. Check the renewal amount in Manage billing before the renewal date.

Connecting Gmail or Outlook before Cassie can sort anything

Inbox Manager needs a Gmail or Outlook connection first, and those are the only two email services Sintra supports. Sintra talks to them through the Google and Microsoft APIs, so a mailbox that reaches Gmail or Outlook over IMAP, POP3 or SMTP will not work, and there is no date for other providers. Cassie can hold a Gmail and an Outlook connection at the same time. In a team workspace, email connections are personal: each member links their own mailbox, and helper chats stay private to the person who started them.

Company accounts add one step. A Google Workspace admin has to enable trusted permissions for the Sintra integration before Gmail connects. On the Microsoft side, Cassie needs mail read and send scopes; work or school accounts may need admin approval, and personal Microsoft accounts get narrower API access than work ones. If someone else runs your domain's admin console, send them the request before you pick a start date. Ask early. A stalled consent screen is the most avoidable delay in the whole setup.

What the eight categories do, and the three that get drafts

Once connected, Inbox Manager sorts incoming mail into 8 pre-defined categories and applies them as labels inside your Gmail or Outlook account ^[2]. The categories are fixed. You cannot rename them, add your own or change the sorting rules. Cassie writes reply drafts for only three of the eight: To Respond, Cold Email and Awaiting Reply. Mail in the other five keeps its label and stays visible only in Gmail or Outlook, where you deal with it yourself.

Drafts land where you already work. Emails that need an answer arrive with a generated draft in the drafts folder of your mailbox, and the same draft shows up in the Inbox Manager inside Sintra. You review it, edit it and send it from chat, from the Inbox Manager, or straight from Gmail or Outlook. Cc and Bcc work. Attachments do not. Neither Inbox Manager drafts nor emails written in chat can carry files or images, so an answer that needs an invoice or a PDF guide still needs a manual step in your mail client.

You steer tone in two places: custom instructions in the Inbox Manager settings, or a plain conversation with Cassie. Sintra's help center says learning from your feedback on replies is not available yet. Your edits today do not shape tomorrow's drafts. Some Sintra marketing pages describe Cassie as learning from approved replies, but the help center article on Inbox Manager is the more specific source and says otherwise. Until that changes, draft quality depends on two things you control: the instructions you write and the snippets stored in Brain AI.

Feeding Brain AI the answers you want Cassie to reuse

Brain AI is the shared knowledge store every helper reads, one per workspace, and it is where Cassie finds your refund rules, opening hours and product details. Integrations do not feed it automatically. Google Drive and Notion pages are not synced live, so a policy that lives only in a shared doc stays invisible to Cassie until you save it into All Knowledge. Files can be up to 20 MB each, in formats such as PDF, DOCX, TXT, Markdown, CSV and XLSX. Scanned PDFs without copyable text cannot be read.

Save exact wording by hand. When you ask a helper to save something from a chat, Brain AI stores a summarized snippet, which works for background context and is risky for a returns policy. Sintra advises adding brand guidelines and legal text manually so the words stay intact. It also admits hallucinations cannot be removed completely, including a helper inventing tasks or abilities it does not have. Its own advice is specific prompts, a check of each output and a new chat when answers drift. Deleting knowledge is final, with no undo.

Facebook Commenter: page comments, one batch at a time

Cassie's second automation drafts replies to comments on a connected Facebook Page ^[3]. It works on Pages only, and it answers only the first comment in a conversation; replies under that comment get no draft. Drafts post only after you approve them, and you can edit or skip each one. You must clear the queue before the next batch arrives: every pending comment has to be approved or skipped first. A page with steady comment traffic therefore needs someone clearing the queue regularly, because the next batch waits until it is cleared.

Connecting the page has its own prerequisites. You log in with a personal Facebook profile, and the Page must be linked to a Meta Business profile. Each workspace connects one Facebook Page, so a second brand means a second workspace. Credit use per reply is light: Sintra lists a reply at about 0.1 credit, and it can change credit costs. The wider credit picture, including what happens when the monthly allowance runs out, sits in our Sintra buyer's checklist.

Where Cassie stops: no chatbot, no DMs, no auto-send

Here the limits are firm. Cassie cannot run as a live chatbot and cannot be embedded in a website, a Shopify store or WordPress, and Sintra gives no date for either. Her responses stay inside the Sintra app. WhatsApp is not among Sintra's integrations. For LinkedIn, Facebook and Instagram direct messages there are no automated replies: Cassie drafts an answer and you copy and paste it into the conversation yourself. Sintra's help center states the rule broadly. Helpers cannot respond to customers on their own, whether through DMs, comments or any other channel.

One exception sits outside Cassie's automations. A recurring scheduled task you create yourself runs with no approval step, so a task set to send an email does send it, and each run costs credits. Sintra's Gmail page mentions scheduled tasks that send weekly customer updates. That is a timetable you wrote, not a reply to incoming mail, and Sintra's Terms treat any action an AI assistant starts as authorized by you. How tasks and automations differ is laid out in our guide to how Sintra's helpers work.

Two neighbors cover jobs people often expect from Cassie. A morning overview of the inbox belongs to Vizzy, whose Daily Summarizer sends a summary of mail and calendar at a time you choose and needs Gmail or Outlook with the matching calendar. Sintra's pricing page also says Milli hands sales follow-ups to Emmie and Cassie. Neither changes the rule above. Drafts still wait for you, whichever helper wrote them.

Telling customers they are reading AI-assisted replies

Sintra's Terms put a duty on you. Businesses that use Cassie as a support agent must tell their end customers, prominently, that they are dealing with an AI, and must update their own privacy policy ^[4]. The EU version of the Terms adds that you must disclose to your users that content is powered by Sintra and its AI engines. The Terms do not say where that notice goes. A line in your email signature and on your contact page is a sensible start; ask your own adviser what prominent means for you.

The Terms also say AI outputs can be inaccurate, biased or fictional, and that all outputs and agent actions need human oversight. Keep sensitive details out of what you feed Cassie. Sintra asks customers to remove personal details before uploading and not to submit health, genetic or biometric data unless safeguards are agreed in writing. For a clinic or a law office, that rules out pasting patient or client files into Brain AI. Approval is not a formality here. It is the control the contract assumes you use.

Will Cassie cover a small support inbox?

Cassie fits as a drafting assistant for a Gmail or Outlook inbox and a single Facebook Page, run by someone who approves replies regularly. She sorts mail into fixed buckets, drafts the three kinds of email that need an answer, and queues page comments in batches. She does not talk to customers directly, attach files, answer DMs or learn from your edits yet. If your support depends on live chat, WhatsApp or replies sent around the clock, she does not fit. No Sintra setting changes that today.