Function deltachat::smtp::send_mdn_msg_id

async fn send_mdn_msg_id(
    context: &Context,
    msg_id: MsgId,
    contact_id: ContactId,
    smtp: &mut Smtp
) -> Result<bool>

Tries to send MDN for message msg_id to contact_id.

Attempts to aggregate additional MDNs for contact_id into sent MDN.

On failure returns an error without removing any smtp_mdns entries, the caller is responsible for removing the corresponding entry to prevent endless loop in case the entry is invalid, e.g. points to non-existent message or contact.

Returns true on success, false on temporary error.