Mails in spam folder all going blank

Mails only a couple months old that stay in my spam folder are going blank. I have some important old mails in there from before I started using spamsieve that are all gone blank. How can I recover these and stop the future emails going blank?

SpamSieve does not change the contents of your messages. I’m not sure which mail program you’re using, but it might help to rebuild its database. Also, if you’re using IMAP or Exchange, you could check (via Webmail or another mail program) whether the copies of the messages on the server are complete.