The mail cache

This page shows how to turn on the mail cache, encrypt it and limit its size. The cache keeps a copy of what Tilde reads, so a big remote mailbox is faster to list and you can search it. The complete list of keys is in config.toml: cache, pgp.

Turn it on

The cache writes mail on your disk, so it is off until you turn it on:

[cache]
enabled = true
size_max = "1GB"
encrypt_key = "#{pass show tilde/cache}"

Key	Meaning	Default
enabled	Turns the cache on.	false
size_max	The largest size of the cache file of one account.	"1GB"
encrypt_key	The key that encrypts the cache files.	none, not encrypted

size_max is a number and a unit, KB, MB or GB, in any case: "500MB", "1.5 GB". A number without a unit is an error, and tcli check shows it. A kilobyte is 1,024 bytes.

What it keeps

• The headers of the folders you opened, and the list of the folders.
• The whole message once you open it. A message you opened is still readable when the server is not reachable.
• An index of the sender, the subject and the body, for the search.
• One file for each account, cache/<id>.db in the root folder of Tilde (~/.config/tilde/cache by default). The id of the account is the name of the file, so an id with other characters than letters, digits, ., _ and - gets no cache.

IMAP accounts keep all of this. A Maildir account is already on your disk, so its cache is an index for the search only. Chat is not cached.

Encrypt it

With encrypt_key the whole file is encrypted, the index included: the subjects, the senders and the bodies are not readable in the file. Only the cache is protected. The configuration and the logs stay readable.

Keep the key in a password manager and read it with #{command} or ${NAME}: see Passwords. Without a key the file is a normal SQLite file, and Tilde logs one warning when it starts (see Logging and jobs).

• A wrong or changed key, or a file that is not a cache: the cache of that account stays off, the file is not touched and the log says which file. The store works without the cache.
• A key added to a plain cache: the file is made again, encrypted and empty.
• Key rotation is not supported. After you change the key, delete the old file with tcli cache reset <account>.

Limit the size

After a message is saved, the cache drops the whole messages that were used least, oldest first, until the file is a little under size_max. Headers, folders and the index of senders and subjects are never dropped. A message larger than the limit is read through and not kept.

Leave an account out

Put cache = false in the store settings of the account. no, off and 0 mean the same.

[accounts.mail.store.settings]
host = "imap.example.org"
cache = false

Fill it and search it

The search covers what the cache holds. These commands fill it and search it with Tilde closed, because two programs would write the same file:

tcli cache rebuild work
tcli cache search work "fat nov"

Every word must match and each one matches as a prefix, so fat nov finds “Fattura di novembre”. The details of the four tcli cache commands are on The cache.