Email with offlineimap

This approach downloads an (offline) copy of the entire IMAP mailbox[^not-backup].

offlineimap

Using the following configuration for offlineimap (~/.offlineimaprc is the default, but I’m locating it with my backup mailbox), I can copy the entire contents of the IMAP account.

[general]
accounts = my-example-acct
metadata = /mnt/backups/offlineimap/metadata

[Account my-example-acct]
localrepository = my-example-Local
remoterepository = my-example-Remote

[Repository my-example-Local]
type = Maildir
localfolders = /mnt/backups/offlineimap/my-example-acct/robin
sync_deletes = no

[Repository my-example-Remote]
type = IMAP
sslcacertfile = OS-DEFAULT
remotehost = imap.example.com
remoteuser = my-username

• sync_deletes = no in the Local section is saying “even if the remote mailbox deletes messages, don’t delete from my copy”.
• sslcacertfile = OS-DEFAULT tells offlineimap to use the OS provided CA certs for verifying the IMAP server’s certificate(s).

Then I can run offlineimap as a one-off with:

offlineimap -c /mnt/backups/offlineimap/offlineimaprc --ignore-keyring -o

And then we’re done, right? If I just do this regularly (by hand, as a cron job, or with something like systemd) then I’m good?NO

What if another client (i.e. a “regular” email client such as Thunderbird) modifies my messages¹ in the source mailbox on the server, perhaps because of a bug, but more likely because of user error(PEBKAC)? Offlineimap will happily sync those bad changes to my local copy and my “backup” provides no value over my regular client.

Actual Backup

Now that we have a one-off copy of the data, let’s add some functionality so that we have actual backup capability.

See https://www.offlineimap.org/doc/backups.html