Function rfc724_mid_download_tried 

pub(crate) async fn rfc724_mid_download_tried(
    context: &Context,
    rfc724_mid: &str,
) -> Result<bool>

Returns true iff there is a message with the given rfc724_mid and a download state other than DownloadState::Available, i.e. it was already tried to download the message or it’s sent locally.