Function deliver_with_headers 

pub async fn deliver_with_headers(
    client: &Client,
    inbox: &Url,
    body: &[u8],
    key: &SenderKey,
    first: Scheme,
    extra: &[(String, String)],
) -> Result<Scheme, DeliveryError>

deliver, with extra headers sent beside the signature’s, such as a Collection-Synchronization header (FEP-8fcf). They are not signed.

Errors

As deliver.