Function spam_target_folder_cfg

async fn spam_target_folder_cfg(
    context: &Context,
    headers: &[MailHeader<'_>],
) -> Result<Option<Config>>

Returns target folder for a message found in the Spam folder. If this returns None, the message will not be moved out of the Spam folder, and as fetch_new_messages() doesn’t download messages from the Spam folder, the message will be ignored.