Because headers are so easy to forge, the email address information is no longer a basis used for blocking spam. Despite this, forging headers remains a common practice among spammers and still constitutes a problem. This not only makes it difficult for a machine to tell which emails to block and which to let through, the spam looks like it originates from a domain not involved in spamming in any way. This results in spam complaints against innocent parties and can create a great deal of trouble for the owners of the faked domain names.