I am afraid the only way to protect your e-mail from receiving unwanted files is not to use it. Otherwise, you cannot avoid it. Many worms (when activated) scan the harddisk for e-mail addresses. If a user gets infected and e.g. has your page (with your e-mail) in the browser cache… the virus can find it and send itself to the address.

Do you remember the exact filenames of the reported trojans?