I find restic a convincing tool for encrypted incremental backups.
It supports a huge number of backends - in the following sftp is used.

As an example, I show how I backup my ~/.mail (which is fetched by mbsync in maildir format).

Initialization

Before we can store our data, we have to initialize a restic repository:
restic -r sftp:user@remotehost:/path/to/storage/mail init
Restic will now let you set the encryption passphrase.

Backup

Now we can start our first backup operation:
restic -r sftp:user@remotehost:/path/to/storage/mail backup ~/.mail --exclude=".notmuch/" --exclude="*.mbsyncstate"
The exclude arguments in this example are used to avoid copying the state files of mbsync and the index created by notmuch.

Subsequent backups are issued the same way and are performed in an incremental way.
Each backup is represented by a snapshot in the restic repository.

List

List all snapshots:
restic -r sftp:user@remotehost:/path/to/storage/mail snapshots

Restore

If we want to restore a snapshot, we just retrieve the hash with the above command and issue a restore:
restic -r sftp:user@remotehost:/path/to/storage/mail restore HASH --target /tmp/restore-mail

Another convenient way to access the backups is the ability to use fuse mounts:
restic -r sftp:user@remotehost:/path/to/storage/mail mount /mnt/restic-mail

Scripting

If you want to trigger your backups with cron or systemd-timers, you might be looking for a way to automatically provide the encryption passphrase.
This can be done by storing the passphrase in the RESTIC_PASSWORD shell variable, but please make sure that’s really what you want to do.