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A privacy-focused email analyzer does not need to collect your mailbox password. For Gmail, it can send you through Google’s OAuth authorization flow, request only the access its features need, and process selected email data on your device. That can keep the analyzer operator from receiving your password or mailbox contents—but local-first design is not, by itself, proof of security.
Why an email analyzer should not ask for your mailbox password
Your email password unlocks far more than a single analysis feature. Giving it directly to another app also makes that app a place where your password could be exposed or mishandled. A provider authorization flow offers a different approach: you sign in with the email provider, review the access requested, and authorize the app without handing the app your password.
For Gmail API requests, Google requires OAuth 2.0 credentials. The app receives an authorization result that can be used to request API access. This changes who handles the password, but it does not mean the app has no access or holds no credential: an authorized app may receive tokens that let it access data within the granted scope.
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In a server-side OAuth flow, the app can receive a one-time authorization code and exchange it for an access token; an offline server-side flow can also receive a refresh token for later use. If the operator’s server receives and stores those durable tokens, the server remains part of the credential trust boundary. Google documents this flow in its Gmail API server-side authorization guide.
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A local-first desktop design can instead direct authorization through the system browser and have the device connect to the provider. Corresync describes using OAuth 2.0 with PKCE and a loopback redirect, with provider requests made directly from the device over TLS. That is a project’s description of its own implementation, not an independent security audit or a guarantee about all desktop OAuth flows. Its privacy policy also describes keeping grants or standards credentials in an OS keyring or approved helper.
The practical question is not simply whether a product says “OAuth” or “local-first.” Ask which component receives the authorization response, whether a backend ever sees a code or token, and where any long-lived grant is stored.
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Choose the narrowest access that supports the feature
OAuth does not automatically mean limited access. The authorization scope determines what an app is allowed to request, so a sound design maps each feature to the minimum provider access it requires. Google’s OAuth 2.0 policies say developers should use only necessary scopes and require a registered OAuth client for each platform.
For Gmail, the API and the mail protocols have an important scope difference:
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| Access route | Scope detail | Design implication |
|---|---|---|
| Gmail API | Google documents granular restricted scopes; the exact scope depends on the API methods and feature. | Map each feature to its endpoint and confirm the minimum scope. Do not assume a particular scope covers a feature without checking. |
| Gmail IMAP, POP, or SMTP with XOAUTH2 | Google’s guide identifies https://mail.google.com/ as the full-mail scope. |
Use this route only when protocol requirements justify the broader access; consider whether Gmail API scopes can meet the need instead. |
Google specifically directs apps that do not need the full-mail scope to use Gmail API’s more granular restricted scopes. See its XOAUTH2 documentation. These details are Gmail-specific; they should not be assumed to describe Microsoft, Apple, Yahoo, or every IMAP provider.
Be precise about what the analyzer reads
“It analyzes email locally” is too broad to tell a user what happens to their data. A useful disclosure names the fields used for each feature and distinguishes metadata analysis from actions that fetch message content.
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For example, Ciela’s May 2026 privacy policy describes a classification feature that uses sender address and name, subject, snippet, List-Unsubscribe-related headers, timestamp, read state, and labels. It says that feature does not read message bodies or attachments and that results are stored in a local SQLite database encrypted with SQLCipher. The same policy describes a separate sender-triage action that fetches threads, so the classification description should not be read as a claim about every feature. These are product statements, not independently verified findings; see Ciela’s privacy policy.
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- Which message fields are accessed for each feature, including whether bodies or attachments are fetched.
- Whether data or derived results are sent to a server, analytics service, or crash-reporting system.
- What is stored locally, how it is protected, and how a user can delete it.
- How provider access can be revoked and what revocation does to locally stored results.
Local-first reduces one exposure, not every risk
If mail data travels directly between a device and its provider, and analysis results remain on that device, the analyzer operator may not need to hold a copy of the mailbox. That can reduce the amount of data entrusted to the operator. It does not establish that the software is secure, that no telemetry leaves the device, or that local storage is safe from other users or malware on that device.
Likewise, avoiding password collection does not mean avoiding credentials entirely. A local client may hold an OAuth token, or another provider and protocol may require a password or app-specific credential. The relevant disclosure is which credential is used, which code can access it, where it is stored, and whether any server receives it.
Google verification and policy obligations still apply
For Gmail, scope choice affects compliance work. Google’s restricted-scope verification guidance says an app accessing restricted data through a third-party server requires a security assessment. It also says verified restricted-scope apps must reassess compliance at least every 12 months. Verification requirements and timelines can change, so developers should check Google’s current guidance before release.
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