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Privacy Policy

Last updated: 15 October 2026

This policy explains what personal data Sickle handles, why, where it goes and how long we keep it. It covers the Sickle Mac app, the Sickle connector for AI assistants (the MCP server at mcp.sickle.app), the account pages at sickle.app and the website itself.

Sickle is operated by Better Email Ltd, a company registered in England, 4 Belsize Park Gardens, London NW3 4LD, United Kingdom (“we”, “us”). We are the controller of the personal data described here. Questions or requests: support@sickle.app.

The short version

  • Mail you read in the Mac app is downloaded directly from your mail provider to your Mac and stored there. It does not pass through our servers.
  • To connect a mailbox, we store its address, its server settings and the credential needed to reach it (a password, app password or OAuth token) on our servers, so the app and the connector can sign in to it for you.
  • When you connect an AI assistant, it asks for mail; our servers fetch what it asked for from your provider and hand it to that assistant. We do not keep copies. What the assistant does with it is governed by its provider’s terms.
  • We don’t sell your data, don’t use it for advertising and don’t use your email to train AI models.

1. What we collect

Your Sickle account

The email address you sign in with, and your name if your sign-in provider shares it. Sign-in is handled by AuthKit, our own sign-in service at authkit.tech. We keep an internal account ID and which onboarding steps you have completed.

Mailboxes you connect

For each mailbox: its email address, the provider, the IMAP and SMTP server names and ports, and the credential used to sign in — either a password or app-specific password you enter, or OAuth access and refresh tokens issued by Google or Microsoft when you approve Sickle there. We also keep the settings you choose, such as a mailbox’s colour and order.

Your email

  • In the Mac app, messages, attachments and folder information are downloaded straight from your mail provider and stored in the app’s database on your Mac. Mail you send from the app goes straight from your Mac to your provider. We do not receive this content.
  • Through the connector, when an AI assistant you have authorised calls a tool (for example “search emails” or “read email”), our servers sign in to your mailbox, fetch only what that call asks for and return it to the assistant. When an assistant you have allowed to send email sends one, our servers hand it to your provider’s outgoing server and, unless your provider does this itself, file a copy in your Sent folder; a draft is saved straight into your Drafts folder. The content is not stored by us. To keep repeated calls fast, the mailbox credential is held in our server’s memory for up to five minutes.

AI assistants you authorise

Which assistants (for example Claude, Cursor or Codex) you have connected and which permissions you granted them: read (list, search and read mail), change (mark as read, move, move to Trash, save drafts) and send (send email from your account; the send tool is marked so that your assistant’s app asks you to approve each send). These authorisations are held by AuthKit. You can see and revoke them at any time at sickle.app.

Payments

Subscriptions are processed by Stripe. We store your Stripe customer ID and subscription status. We never see or store your full card number.

Feedback and support

If you send feedback from the app, we receive your message and your account email address; it is delivered to our team chat through Telegram. Emails to support@sickle.app are forwarded by Cloudflare to our inbox, which is hosted by Google.

Usage, diagnostics and logs

  • Website: LogSnag records page visits and clicks on key buttons, with a random visitor ID kept in your browser, the page, the site that linked you here and any campaign tags in the link. Ahrefs Web Analytics counts page views without cookies.
  • Mac app: LogSnag records a few usage events (such as the app being launched) linked to your account ID. Crashes and errors are reported to Sentry, hosted in the EU, configured not to include personal information such as your IP address; reports contain technical details about the error, the app version and your Mac.
  • Sender icons: to show a sender’s logo, the app asks our server for the icon of the sender’s domain (for example “example.com”, not the full address). Icons are cached by domain for up to a day.
  • Updates: the app checks storage.sickle.app for new versions, which shares your IP address and app version with that server.
  • Server logs: our servers log requests with their time, path, status and IP address, to keep the service running and secure. Mailbox credentials and email content are not written to these logs.

Cookies and browser storage

sickle.app uses a cookie to keep you signed in to your account pages, and our network provider may set strictly necessary security cookies. The website keeps a random visitor ID and details of your current visit in your browser’s storage for the analytics above. We use no advertising cookies or cross-site trackers.

2. How we use it, and our legal bases

  • To provide Sickle — signing you in, connecting your mailboxes, running the connector for the assistants you authorise, and billing. Legal basis: performance of our contract with you.
  • To keep it secure and working — preventing abuse, investigating faults, fixing crashes. Legal basis: our legitimate interest in running a reliable, secure service.
  • To understand and improve the product — aggregate usage and which pages and links bring people to Sickle. Legal basis: legitimate interests.
  • To answer you — support requests and feedback. Legal basis: contract and legitimate interests.
  • To meet legal obligations — for example keeping billing records.

We do not sell personal data, share it for advertising, build advertising profiles, or use your email content to train or improve AI or machine-learning models.

3. Data from Google and Microsoft accounts

When you connect a Gmail or Google Workspace mailbox, Sickle asks Google for access to your mail (the https://mail.google.com/ scope) so it can show, organise and send your mail in the app and, if you connect an AI assistant, fetch the mail it asks for and send or save the email you allow it to. Sickle’s use and transfer of information received from Google APIs adheres to the Google API Services User Data Policy, including the Limited Use requirements. In particular, we:

  • use Google user data only to provide the features you see in Sickle;
  • transfer it to others only to provide those features at your direction (such as returning mail to an AI assistant you connected), for security, or to comply with the law;
  • never use it for advertising, never sell it, and never use it to train generalised AI or machine-learning models;
  • do not let people read it unless you ask us to (for example to fix a problem you report), it is needed for security or to comply with the law, or it is aggregated and anonymised for operations.

Microsoft mailboxes (Outlook, Hotmail, Microsoft 365) are connected the same way, with access to read mail over IMAP and send mail over SMTP, and the same limits apply.

4. AI assistants and the connector

The connector lets an AI assistant you choose work with your mailboxes. You decide which assistant to connect and which permissions to grant, and you can revoke access at sickle.app at any time. When the assistant calls a tool, the mail it receives becomes part of your conversation with that assistant and is handled under its provider’s terms and privacy policy (for example Anthropic for Claude, OpenAI for Codex, Anysphere for Cursor). We don’t control what those services do with it. Email is written by other people, so treat its content with the same care you would any untrusted text you give an assistant.

5. Who we share data with

We use these service providers, who process personal data on our behalf and only for the purposes above:

  • Hetzner — the servers that run Sickle’s backend and database. European Union.
  • Cloudflare — network delivery, security and DNS for sickle.app, and forwarding of email sent to sickle.app addresses. Global network.
  • Stripe — payments and subscriptions. United States and European Union.
  • Sentry — crash and error reports from the Mac app. European Union.
  • LogSnag — product and website usage events.
  • Ahrefs — cookieless website analytics.
  • Telegram — delivers in-app feedback to our team chat.
  • Google — hosts the inbox that receives support email.

Your mail providers (such as Google, Microsoft, Apple, Fastmail or your company’s mail server) and the AI assistants you connect are not our service providers: we pass data to them because you asked us to connect them. We may also disclose data if the law requires it, to protect people’s safety or our rights, or to a buyer if Sickle is sold, in which case this policy continues to apply.

6. International transfers

Our servers are in the European Union. Some providers above process data in other countries, including the United States. Where personal data leaves the UK or the EEA, we rely on the safeguards those providers offer, such as the UK International Data Transfer Addendum and the EU Standard Contractual Clauses.

7. How we protect it

Traffic between the app, the website, AI assistants and our servers is encrypted in transit with TLS, and connections to mail providers are encrypted wherever the provider supports it. Access to production systems is limited to the people who operate Sickle. The connector only accepts requests carrying a valid, unexpired authorisation, and each tool checks the permission it needs. No system is perfectly secure; if a breach affects your personal data, we will tell you and the regulator as the law requires.

8. How long we keep it

  • Account and mailbox data — while your account exists. Removing a mailbox deletes its stored credential straight away.
  • Deleting your account — email support@sickle.app from your account address and we will delete your account and mailbox data within 30 days, except records we must keep by law.
  • Billing records — as long as the law requires; in the UK, generally six years.
  • Mail in the Mac app — on your Mac until you remove the mailbox or the app’s data.
  • Mail fetched, drafted or sent by the connector — not retained by us; credentials are held in memory for up to five minutes.
  • Server logs — rotated automatically and overwritten once they reach a fixed size, so they are kept only briefly.
  • Analytics and crash reports — for the retention periods of LogSnag, Ahrefs and Sentry.
  • Feedback and support emails — as long as we need them to deal with your request.

9. Your rights

Under UK and EU data protection law you can ask to access, correct, delete or export your personal data, ask us to restrict how we use it, object to processing based on legitimate interests, and withdraw any consent you have given. Email support@sickle.app; we will reply within one month. You can also remove mailboxes and revoke AI assistants yourself at sickle.app.

If you are unhappy with how we handle your data, you can complain to the UK Information Commissioner’s Office (ico.org.uk) or the data protection authority where you live.

If you live in California or another US state with a privacy law: we do not sell or “share” personal information for targeted advertising, and you can ask to know about or delete the personal information we hold by emailing us.

10. Children

Sickle is not intended for anyone under 16, and we don’t knowingly collect their personal data. If you think a child has given us personal data, contact us and we will delete it.

11. Changes to this policy

We will update this page when our practices change and change the date at the top. If a change materially affects how we use your data, we will tell you by email or in the app before it takes effect.

12. Contact

Better Email Ltd, 4 Belsize Park Gardens, London NW3 4LD, United Kingdom — support@sickle.app.