Double E-Mail for Notifications

For a few weeks now, when someone replies to a thread that I have subscribed to, I get TWO e-mails alerting me to this reply. They aren't immediate either. They are spaced about a minute apart. How do I get this to stop? Sure, it makes me feel like I am a very popular person to have my blackberry going crazy all day but it does get annoying deleting all of those messages.