Privacy Policy

1. Who we are

The controller of personal data processed in connection with Mailer is:

Martin Kukal
U Valu 496, Nupaky, 25101, Czech Republic
E-mail: martin@kukal.cz

We have not appointed a Data Protection Officer. Privacy questions and requests can be sent to the e-mail address above.

2. Scope of this policy

This policy explains what data Mailer processes, why, where it is stored, and what rights you have. It covers the Mailer desktop application for Windows and Linux and this website.

Mailer connects to third-party services you choose, such as your mail provider, Google, Microsoft, an AI provider, or a translation service. Those services process data under their own terms and privacy policies.

3. What Mailer processes

Depending on which features you use, Mailer may process:

Mail may contain special categories of personal data. You decide what to store in your mailbox and whether to use optional features such as AI. Do not use Mailer to process special-category data unless you have a lawful basis to do so.

4. Where Mailer stores data

Mailer does not operate a server that stores your mailbox. The application stores its data locally on your computer:

• Windows: %APPDATA%\Mailer
• Linux: $XDG_CONFIG_HOME/Mailer or ~/.config/Mailer
• Portable build: the folder set by the MAILER_HOME environment variable

The local data folder may contain:

• mailer.sqlite — messages, headers, mailboxes, contacts, calendar, settings, and logs;
• blobs/ and attachments/ — message bodies and attachment files;
• secrets.enc — encrypted passwords and OAuth tokens;
• crashes/ — local crash diagnostics, if a crash occurred.

The secrets vault is encrypted with AES-256-GCM. Its key is sealed by the operating system: Windows DPAPI, Linux Secret Service / keyring, or a machine-derived fallback when the OS keyring is unavailable. Crash reports are stored locally and are not uploaded automatically.

5. Google user data and Limited Use

If you connect a Gmail account, Mailer uses Google OAuth 2.0. The app requests the scope https://mail.google.com/ together with openid, email, and profile. The Gmail scope allows Mailer to read, send, and manage your Gmail messages through IMAP and SMTP.

Mailer uses Google user data only to provide the email functionality you request, including:

• signing in to your Google account and obtaining an access token;
• fetching, displaying, searching, organising, sending, and deleting your mail at your direction;
• keeping your account connected through token refresh.

Mailer does not use Google user data for advertising, marketing, profiling, sale, or resale. Mailer does not use Google user data to train general-purpose AI models. Mailer does not allow humans to read your Google user data, unless you explicitly ask for support and send us the relevant content, or unless required for security or legal reasons.

Google user data is stored locally on your device. It is transferred to third parties only when necessary to provide a feature you request — for example, to your chosen AI provider when you explicitly use an AI feature — or when required by law. Google itself processes authentication data under its own privacy policy.

You can revoke Mailer's access at any time at myaccount.google.com/permissions. Disconnecting the account in Mailer also removes the locally stored tokens.

6. Microsoft and other mail providers

For Microsoft 365, Outlook.com, and other Microsoft accounts, Mailer uses Microsoft OAuth 2.0 with the delegated scopes needed for IMAP and SMTP. For other providers, Mailer uses the IMAP/SMTP credentials you enter. Your mail provider processes your mail under its own terms.

7. Optional AI features

AI features are optional. They run only when you configure an AI provider and use an AI action such as triage, reply drafting, translation, chat, or a task. Depending on the action, Mailer may send the prompt and the message context needed for that action — for example the subject, sender, snippet, body text, or selected text — to the provider you configured.

Supported providers include OpenAI, Anthropic, Google Gemini, DeepSeek, Groq, Mistral, xAI, OpenRouter, and OpenAI-compatible custom endpoints, including local models. The provider's own terms and privacy policy apply. Do not enable AI for content you do not want to send to that provider.

AI output may be inaccurate. Mailer does not use AI to make automated decisions with legal effects about you. You review and decide what to send or keep.

8. Translation

If you use the free MyMemory translation engine, the text to be translated is sent to MyMemory (translated.net). If you choose an AI translation engine, the text is sent to your configured AI provider instead. Translation results are cached locally.

9. Remote content, images, and tracking links

Remote images and known tracking links in HTML mail are blocked by default. If you choose to load remote images or allow tracking links, your device connects directly to the sender's servers, which may see your IP address, user agent, and the fact that you opened the message.

10. Updates

Mailer checks for updates from GitHub. The request may include your IP address, user agent, and the app version. GitHub processes that data under its own privacy policy. Mailer does not send your mail content as part of the update check.

11. OpenPGP keyserver

If you ask Mailer to fetch a public PGP key by e-mail address, the address is sent to keys.openpgp.org. Do not use this feature if you do not want the address sent to that keyserver.

12. This website

This website does not use cookies, analytics, advertising trackers, or social media embeds. To remember your chosen appearance, it stores one functional value in localStorage: mailer-theme with the value light or dark. This value is not sent to us, contains no identifier, and is not used for tracking. It is set only when you choose the light or dark theme. You can delete it by clearing site data; the site will then follow your system setting again. This is user-requested functional storage, so the site does not show a cookie consent banner. The web server may process standard technical data such as your IP address, user agent, and requested URL in temporary logs for security and troubleshooting. We do not use that data to profile visitors or to build marketing audiences.

13. Legal bases

Where the GDPR applies, we rely on:

• Performance of a contract — to provide the app's core mail, calendar, and security features you request.
• Legitimate interests — to keep the app secure, prevent abuse, and diagnose failures.
• Consent — for optional features that send data to third parties, such as AI and translation, where consent is required.
• Legal obligation — where we must retain or disclose data by law.

14. Sharing and processors

We do not sell personal data. Data may be processed by:

• your mail provider (for example Google or Microsoft) to send and receive mail;
• the AI provider you configure, when you use an AI feature;
• MyMemory, when you use free translation;
• GitHub, for update checks;
• keys.openpgp.org, when you fetch a PGP key;
• our hosting provider, for the technical operation of this website;
• authorities or courts, where required by law.

If you contact support, we process your message and any files you choose to send. Please do not send more than necessary.

15. International transfers

Some providers may process data outside the European Economic Area. Where required, transfers rely on an adequacy decision or standard contractual clauses offered by the provider. You choose which optional providers to use; their privacy policies describe their safeguards.

16. Retention and deletion

Local data remains on your device until you delete it. You can remove an account in the app, delete individual messages, or delete the whole Mailer data folder. Uninstalling the app may not remove the data folder automatically.

To remove local data completely:

1. Remove the account in Mailer, or delete the Mailer data folder (%APPDATA%\Mailer on Windows, ~/.config/Mailer on Linux).
2. Revoke Mailer's access in your Google or Microsoft account settings.
3. Delete any support e-mails you sent us when they are no longer needed.

Your mail provider may retain copies of messages, backups, and logs under its own retention rules. Mailer cannot delete data held by your provider.

17. Security

Mailer uses TLS for network connections, an encrypted local secrets vault, and OS-bound key storage. Remote content is blocked by default. No system is perfectly secure: protect your device account, use a strong login, and keep your operating system and Mailer updated.

18. Your rights

Where the GDPR applies, you have the right to:

• access your personal data and obtain a copy;
• correct inaccurate data;
• erase data, subject to legal exceptions;
• restrict or object to processing;
• data portability;
• withdraw consent for optional processing;
• lodge a complaint with a supervisory authority.

The Czech supervisory authority is the Office for Personal Data Protection (Úřad pro ochranu osobních údajů), Pplk. Sochora 27, 170 00 Prague 7, www.uoou.cz. You can also contact your local EU authority.

To exercise your rights, e-mail martin@kukal.cz. We may need to verify that the request comes from you.

19. Children

Mailer is not directed to children under 16. Do not use the app to create accounts for children without the consent required by your local law.

20. Changes to this policy

We may update this policy when the app or the law changes. The effective date at the top of this page will change, and material changes will be announced in the app or on this website.

21. Contact

Privacy questions, data requests, and security reports: martin@kukal.cz.

This policy is available in English and Czech. For users in the Czech Republic, the Czech version prevails if there is a conflict.