How to remove duplicate mails?

[squonk]

I've got a serious issue with Zimbra. I don't know what happens, but after a backup of my mails my computer freezed within a syncronization and I've lost many mails.
So I've made a restore of the last stable situation, but I don't know why now I've got ALL my mails duplicated 3 TIMES in my yahoo account in ALL my folders!

So I ask you: ho can I remove all the unwanted copies?
I hope that it is a simple way...

Many thanks!

[squonk]

More than one year ago I've tried Zimbra, but with no luck. After the unsolved problem of duplicated mails I've removed Zimbra from my pc.
Today I've downloaded the new version and installed it on my pc.
But the problem of duplicated mails is always there.
Can someone help to remove quickly thousands duplicated mails?

Many thanks!