Sync and devices

How sync works

Sync needs a Letos account. Changes on one device reach your other devices through our sync server (relay).

• End-to-end encrypted. Every change is encrypted right on the device with a key the server doesn’t know. The server only stores and forwards encrypted packets. Details in Privacy and security.
• What syncs: tasks and their attachments, mail triage state (archive, snooze, reminders), sender rules, app settings, calendar visibility, and the setup of your mail and calendar accounts (including sign-in details, encrypted).
• What doesn’t sync: the content of e-mails and events — each device downloads them itself, directly from the provider. Also unfinished drafts, AI API keys, agent (MCP) settings and window layout.
• How fast: your other devices are told about a new change almost immediately; otherwise Letos syncs with the server regularly on its own.
• iPhone in the background: when Letos is closed or in the background on your iPhone, the server sends it a silent signal through Apple after a change from another device. The signal carries no content, only “something is new”, and the iPhone then briefly downloads the changes itself. Nothing is shown and nothing makes a sound. There are only a few signals per hour, and iOS may delay them (for example in Low Power Mode, or after you force-quit the app). Opening Letos always catches up right away.

Offline

Letos works offline too. Changes are saved on the device and sent as soon as you reconnect (“Offline — changes will be sent as soon as this device reconnects.”). Mail that’s already downloaded stays readable.

Adding another device

1. Install Letos on the new device.
2. On the start screen choose I already use Letos → sign in.
3. Sign in with your e-mail and password (and a verification code if you use two-factor authentication).
4. Letos downloads your settings and data. Mail and calendar are then downloaded directly from the provider.

How many devices you can have depends on your plan (see Pricing). If you’re at the limit, remove an old one from another device first.

Managing devices

Settings → Letos account → Devices. You’ll see a list of devices with this device marked. You can rename a device (Device name) or Revoke access — it’s then signed out and stops syncing.

Signing out

Settings → Letos account → Sign out.

On the computer and the iPhone, signing out asks Sign out and delete data from this device? Tasks, e-mails, calendars, attachments, connected mail accounts and their passwords are deleted from this device. Nothing is deleted on the Letos server or at your mail provider — after signing in again the data is downloaded again. Appearance and layout stay.

If there’s something on the device that hasn’t been sent yet (unsent changes, e-mails in the outbox, unfinished drafts, attachments not uploaded), Letos lists it and offers Send first (tasks, mail, attachments). Only then choose Sign out and delete data.

On the web, signing out only ends the sign-in in your browser; your data stays.

Signing out leaves the device in your device list. If you sign in again, it takes another slot until you remove the old one.

If you sign in on a device with a different Letos account, the previous account’s data is deleted from it first. Letos warns you about this.

Deleting your account

Settings → Letos account → More options (at the very bottom) → Delete account. The action is hidden on purpose. After you click it, an explanation of what is and is not deleted comes first; you enter the password only after I understand, continue.

On the server, this permanently deletes your account and sign-in details, all paired devices, the encrypted sync data (tasks, rules, settings) and attachments stored on the server. Your plan and the invites you sent are deleted too. You confirm with your password (and verification code), by typing the word DELETE, and with the Permanently delete account button, which stays disabled until the word matches.

All local data on the device you delete the account from is deleted too — downloaded mail, calendar, tasks, settings and the saved passwords and access tokens for your accounts — and the device is signed out. Your mailboxes at your e-mail provider and your calendars at Google stay as they are. A subscription with the payment partner is not cancelled automatically. Deletion can’t be undone.