We’ve made the difficult decision to discontinue the Yahoo Communities effective Jan 24, 2019.
Be assured you will still be able to find answers to your Yahoo product and app questions on the Yahoo Help website (https://help.yahoo.com). In addition, you’ll be able to find the Yahoo Community moderators on Twitter, responding from our many handles including @YahooCare and @YahooFantasyCC.
If you ever need help with your Yahoo accounts, try Yahoo Account Pro for 24/7 live phone support.
Sometimes when emails duplicate like this it's due to syncing issues between the account and a mail app. If you access the account through a non-Yahoo app, you may want to remove the account from the device and re-add it to resolve any future syncing issues.