Offline mail — Nixt Mail docs

Offline mail keeps a copy of your mail on this computer so you can see and read it with no internet connection — on a train, on a plane, or when your provider is down.

It is off until you turn it on. When it is on, the copy is encrypted, never sent anywhere, and deleted when you remove the account.

What can be kept

For each account and folder you choose how much to keep:

Choice	What is kept	Shown in Settings as
Off	Nothing is kept on this device. Every launch fetches from the server.	Off
Headers only	Senders, subjects and dates, the first line of each message as the list shows it, whether you replied, and the identifier of each conversation. Enough to see your mail offline, but not to read it: the rest of each message is not stored.	Headers
Full messages	Headers, plus the text of messages you open, so you can read them again with no connection. Their text is stored on this device.	Full

And for how long:

Choice	Keeps mail from
A day	The last day.
A week	The last week.
A month	The last month. This is the starting choice.
Three months	The last three months.
A year	The last year.
Until I remove the account	Any time. Nothing expires.

Mail older than the period you chose is removed from this device. Nixt Mail checks about once an hour while anything is kept, and whenever you change a choice.

Turn on offline mail

Open Settings › Sync and offline.
Find the Offline mail card.
On the Default row — For any account not set below. — choose Headers or Full.
Choose how long to keep mail from the menu beside it. The menu appears once you choose anything other than Off.

A sentence under the Default row describes what the chosen level keeps.

Every account now follows the default. Each change takes effect straight away.

Set an account differently

Under PER ACCOUNT, every account is listed by address. An account that follows the default says Following the default.

On the account’s row, choose Off, Headers or Full.
Choose how long, from the menu beside it.

An account’s choice is a ceiling for its folders: no folder can keep more than its account, or keep it for longer. An account set to Off keeps nothing at all, whatever its folders say.

Set a folder differently

Folders can be set for the account that is open in the sidebar.

Open the account whose folders you want to set.
In Settings › Sync and offline › Offline mail, choose Per folder. It shows, for example, 12 folders, all following the account or 2 of 12 set separately.
On a folder’s row, choose Off, Headers or Full, and how long.

The list says A folder can keep less than its account, never more. If the account is set to Off, it says This account keeps nothing, so its folders keep nothing. and the folder rows are greyed out.

If a folder asks for more than its account allows, the account’s limit is used.

Reading with no connection

When an account has no connection and mail is kept for the folder you open:

The sidebar lists the folder names Nixt Mail last saw.
The message list shows the kept mail, with a line at the top: Offline. Showing the mail kept on this device. — or, once the copy is at least two minutes old, Offline. Showing mail saved followed by how long ago, such as 20 minutes ago, 3 hours ago or 2 days ago.
Reconnect on that line tries to connect again straight away.
Search looks through the kept mail of the folder: senders, subjects, the opening lines of each message, whether it has a file, and read or unread. is:flagged and larger: need the server, so they find nothing offline.
Opening a message whose text was kept shows it. A message whose text was not kept says This message has not been kept on this device. Reconnect to read it, or turn on offline mail in Settings to keep the ones you open.

If nothing is kept for the folder, the list shows Connection issue instead. See When the connection drops.

What needs a connection

Kept mail is a copy for reading.

Archiving, moving to the trash, flagging, and marking read or unread change the server, so they need a connection. While offline, a snack bar says, for example, Can’t archive this while offline. This message is the copy kept on this device; reconnect to change it on the server.
Search finds only what is kept, not the rest of the folder on the server.
Sending needs a connection. See Writing mail.

How the copy is protected

Encrypted. Kept mail is encrypted on disk with a key held in this device’s keychain.
Private to Nixt Mail. It is stored in Nixt Mail’s own app storage.
Never sent anywhere. The copy exists only on this device.
Only what you chose. Choices are enforced whenever they change, including choices made tighter while Nixt Mail was closed.

Clear what is kept

To delete the copies without changing your choices:

Open Settings › Sync and offline.
Under Offline mail, beside Mail kept for offline reading, choose Clear. It is greyed when nothing is kept.

The button is replaced by Cleared. Your choices above it are unchanged, and nothing on your mail server is touched. If offline mail is still on, Nixt Mail starts keeping mail again as you use it.

Kept mail is also deleted:

For one account, when you remove that account.
For everything, when you choose Erase everything on this device in Settings › Privacy and security. That also destroys the encryption key, so any fragment left on disk cannot be read.
When you turn a level down. Choosing Off or Headers removes what the new choice no longer allows.

Offline mail and other settings

Offline mail choices are kept apart from your other settings: Restore defaults, Reset all settings and settings files leave them alone. Set them on each computer.
Download messages in advance (in the same section) downloads messages before you open them so they open quickly. It does not keep them; only opening a message keeps its text.
Your calendar has its own offline copy. See Calendar.