Duplicate stories with email newsletters

I use the forwarding email quite a bit to send some of my emailed newsletters to Newsblur. I’ve noticed the majority of these, but not all, end up duplicated when they’re in Newsblur. I get two entries for each email that gets forwarded.

I’ve modified my forwarding rule to send to another email address to see if I’m actually sending two emails out, but I’m not. It’s only sending one out from my provider.

I can’t figure out where the duplicate is coming from. Has anyone else experienced this issue?