The synchronisation of contacts (phonebook items) of Sailfish OS has the following principles (only some of them listed) - this is the current (2018) intended implementation. Some errors may exist...

This is how it used to be till Sailfish OS version

  • There are local contacts and synced contacts.
    • A contact created in the device or copied to the device with Bluetooth or File Manager is a local contact.
    • A contact originally synced down from an account server (e.g. an MS Exchange server or from is a synced contact

  • Also, local contacts are synced up to account servers if the device has one or more such accounts for which option "Two-way sync" is enabled. These up-synced local contacts are still included in the backup. But if option "To device only" is in effect for all accounts (i.e. syncing in the direction from the server to the phone is selected) then all contacts remain unsynced. 
  • Only local contacts are included in the Backup. Since synced contacts can be retrieved from the account server, they are left out from the backup. The pure original down-synced contacts are never included in the backup.
  • When creating a contact or editing a contact there is no way to link it to an account. It can be linked to another contact, though, which might belong to an account, making the first mentioned contact a synced one.

This is new from Sailfish 4 onwards

When creating a new contact in the device, it can be saved to the phone, making it a local contact, or to a service (like Google) making it a synced contact. In other words, there is a new field "Save to" in the contact dialogue.