You can create a Rule to do this.
Go to Menu > Tools > Rules, and select New Rule.
Choose Apply Custom Rule on messages I receive.
Select the with words found in the header option.
Click on the words link and type in: From: .icu
Note the colon and period, so type it exactly as in bold above.
Click on Add and then OK.
Your Rule should look like this:
Click on Finish.
Now any email from the .icu domain will go to the Junk Email folder.