Adding the proper headers such as DKIM, SPF, etc., are used to make sure a spammer can't send mail pretending to be someone else. All spam systems still look a

Adding the proper headers such as DKIM, SPF, etc., are used to make sure a spammer can't send mail pretending to be someone else. All spam systems still look at the content of the message plus the reputation of the IP/domain when determining if a message should be marked as spam or not.