Editing Anti-spam techniques (section)

===Limit email backscatter===
{{Main|Backscatter (email)}}

If a receiving server initially fully accepts an email, and only later determines that the message is spam or to a non-existent recipient, it will generate a [[bounce message]] back to the supposed sender. However, if (as is often the case with spam), the sender information on the incoming email was forged to be that of an unrelated third party then this bounce message is [[Backscatter (email)|backscatter spam]]. For this reason it is generally preferable for most rejection of incoming email to happen during the SMTP connection stage, with a 5xx error code, while the sending server is still connected. In this case then the ''sending'' server will report the problem to the real sender cleanly.