In C1 enter:
=IF(COUNTIF(A:A,B1)0,"a","") and set the font to Marlett

Then copy down

--
Gary''s Student - gsnu200850


"frederico roldao" wrote:

I have a sheet with 3 columns.

On column "A" I have 1000 email addresses, on column "B" I have 200 email
addresses.

On column "C" I want to have a formula that will mark the cell if the
address on the adjacent cell (in column B) also exists somewhere in column A.

How do I go about this?