Mail and duplicate messages in Sent folder

[JokerPower]

Hello!

I have a problem with Mail app, almost every sent message creates duplicate. Any solution to this?

I'm using Hotmail, macOS Sierra latest updates.

Thanks

 

[Apple_Glen_UK]

Hello!

I have a problem with Mail app, almost every sent message creates duplicate. Any solution to this?

I'm using Hotmail, macOS Sierra latest updates.

Thanks

Did you ever find a solution to this as I have the exact same problem and am eager to resolve it?