Offline mail on desktop and Android
Mail is stored on the server. Each device also keeps a copy so recent mail opens instantly and stays readable without a connection. The server is always the source of truth: while a device can reach it, the app reads from the server and the copy is used only when the server cannot be reached.
What the copy contains
Section titled “What the copy contains”| Desktop app | Android app | |
|---|---|---|
| Message list (headers) | 180 days by default | 30 days by default |
| Full messages (bodies) | 30 days by default | 30 days by default |
| Storage cap | 250 MB of message content by default | follows the device free space |
| Attachments | not cached, opened on demand | not cached, opened on demand |
| Calendar, contacts, tasks | cached on the same principle | cached on the same principle |
Each device keeps its own copy, so two devices can differ while both are correct. Nothing is removed from the server by setting a smaller window; the server simply keeps the only full record.
Settings
Section titled “Settings”Desktop app, Settings > Offline mail
- Offline mail: turns the copy on or off for this device.
- Keep message list for: how far back headers are kept. Headers are small, so this can be wide.
- Keep full messages for: how far back bodies are kept for reading offline.
- Storage limit for message content: the cap for bodies on this device.
- Offline mail actions: Download now starts a sync immediately, Delete offline mail removes the copy from this device only.
Android app, Settings > Offline mail
- Cache recent mail: turns the copy on or off. Turning it off removes the copy for that account.
- Delta sync engine (beta): keeps mail in step with the server incrementally instead of re-downloading a window. Switching it clears and rebuilds the copy.
- Message list history and Message bodies: the two windows described above.
- Sync now: runs one sync cycle.
- Rebuild: deletes the copy on this phone and downloads it again. Changes you made offline that have not been sent yet are kept and sent afterwards.
- Clear cache: deletes the copy and keeps nothing pending.
The “showing saved mail” banner
Section titled “The “showing saved mail” banner”An amber banner appears when the last read was answered from the copy instead of the server, including the case where the phone is connected but the server did not answer. It means what is on screen may be older or narrower than the server: newer messages, or a folder that has not been downloaded yet, can be missing. Open Retry or pull the list again once the server answers; the banner clears on the first successful server read.
The banner is not an error state and does not mean mail was lost. It is the app telling you that you are looking at the copy.
When a device disagrees with the server
Section titled “When a device disagrees with the server”If a folder looks incomplete on a phone or on the desktop app while the web shows more:
- Check the banner. If it is visible, the app is reading the copy; retry first.
- Open the folder and pull to refresh. Recent mail is downloaded first for Inbox, Junk and Sent.
- If the gap remains, use Rebuild on Android or Delete offline mail followed by Download now on the desktop. That discards the copy, which is always safe, and downloads it again.
- If a folder is still empty after a rebuild, report the folder name: the copy is a window, so mail older than the window is expected to be absent offline while it remains on the server.
Working while offline
Section titled “Working while offline”- Reading: cached mail opens; anything outside the window asks for a connection.
- Writing: sending, moving, flagging and deleting are queued and sent when the connection returns.
- Conflicts: if the same message changed on both sides, the app asks instead of guessing; pending items appear in Sync conflicts on Android and in the offline actions area on the desktop.
- Search: offline search covers the mail that is on the device; the server answers for the rest once online.
- Attachments: always fetched on demand, so a message can open offline while its attachment cannot.
Privacy
Section titled “Privacy”The copy is encrypted on the device, and the key is held in the operating system’s credential store rather than in the app data. Deleting offline mail removes the copy from that device; the server copy is untouched. Nothing in the copy is shared with another product or another person.