我用的是apache camel，有轮询功能，轮询时我的邮件被标记为已读。

options : delete=false&peek=false&unseen=true

轮询后，当我在处理附件时，如果有任何错误发生，我想使邮件为“未读”。这样我就可以在以后再次池。

public void process(Exchange exchange) throws Exception {
    Map<String, DataHandler> attachments = exchange.getIn().getAttachments();

    Message messageCopy = exchange.getIn().copy();

    if (messageCopy.getAttachments().size() > 0) {
        for (Map.Entry<String, DataHandler> entry : messageCopy.getAttachments().entrySet()) {

            DataHandler dHandler = entry.getValue();

            // get the file name
            String filename = dHandler.getName();

            // get the content and convert it to byte[]
            byte[] data =
                    exchange.getContext().getTypeConverter().convertTo(byte[].class, dHandler.getInputStream());

            log.info("Downloading attachment, file name : " + filename);
            InputStream fileInputStream = new ByteArrayInputStream(data);
            try {
                // Processing attachments
                // if any error occurs here, i want to make the mail mark as unread
            } catch (Exception e) {
                log.info(e.getMessage());
            }
        }
    }
}

我注意到选项peek，通过将其设置为true，它将不会使邮件标记为已读在轮询期间，在这种情况下，有任何选项，使其标记为已读处理后.