Proper syntax for finding duplicates comparing two columns in two sheets

[AtariBaby]

Hi
I think this is pretty simple, it's just that excel formulas break my brain.

I have Column D in Sheet1, and I have Column D in Sheet2. Both columns are for email addresses.

I want to compare the two for duplicates to determine what to delete from Sheet2. I presume countif or similar would work fine by outputting a column of the count, and then I delete all rows greater than 0.

Would someone help me with the best syntax please?

 

[AtariBaby]

oh i might have it actually:

COUNTIF(sheet1!D:D,d2)