Ok, i missed the variable name "@email".

I'm Sorry and, no, i didn't test it

DECLARE @Email VARCHAR(100)

DECLARE @Email2 VARCHAR(100)

Set @email= 'helper@sql-server-helper.com'

set @email2='fff@dd.com, helper@sql-server-helper.com,vc@.com'

SELECT case when @email2 like '%' + @email1 +...