Crontab is re-importing that same email multiple times

Hello,
In EasyDiscuss, whenever a user sends a reply via email, it get re-imported as many times the crontab runs. Once someone sees it and responds back, it looks like it is stopping.. I had setup a cronjob with 30min incremental and in one day there are over 30 same responses. Not sure if this is configuration issue or a bug.

Please advise.