Duplicated messages

Beginning recently I am receiving duplicated messages. My webmail is Gmail, and the messages are not duplicated there. How to stop?

It may be that there is some corruption in the database. The easiest solution is to remove the account from eM Client, then add it again. To remove the account, go to Menu > Tools > Accounts and click on the bin icon next to your account. Then to add the account again, click on the + icon.