Sql Server Email Validation in Store procedure

IF not (

CHARINDEX(' ',LTRIM(RTRIM(@email))) = 0

AND LEFT(LTRIM(@email),1) <> '@'

AND RIGHT(RTRIM(@email),1) <> '.'

AND CHARINDEX('.',@email ,CHARINDEX('@',@email)) - CHARINDEX('@',@email ) > 1

AND LEN(LTRIM(RTRIM(@email ))) - LEN(REPLACE(LTRIM(RTRIM(@email)),'@','')) = 1

AND CHARINDEX('.',REVERSE(LTRIM(RTRIM(@email)))) >= 3

AND (CHARINDEX('.@',@email ) = 0 AND CHARINDEX('..',@email ) = 0)

)

begin

   // TO DO

end