Thank you for your question. We are sorry to hear about your email duplicating, but we have some articles that will help you troubleshoot the duplicates. If the mail is downloading repeatedly, [http://kb.mozillazine.org/Repeatably_downloading_the_same_messages these instructions] will resolve the issue. If the mail is duplicated and needs to be cleaned up, [http://kb.mozillazine.org/Duplicate_messages_received these instructions] will guide you. If you have any other issues, please report back and we are happy to help.