source: https://www.securityfocus.com/bid/12620/info
Biz Mail Form is prone to a vulnerability that allows the application to be abused as a mail relay.
An attacker can exploit this issue to inject arbitrary SMTP headers by using CR and LF sequences.
If successful, it becomes possible to abuse the application as a mail relay. Email may be sent to arbitrary computers. This could be exploited by spammers or other malicious parties.
Update: It is reported that the update to address this issue (Biz Mail Form 2.2) is vulnerable to this issue as well. The affected version is being added as a vulnerable package and the fixes are being removed.
Exploit Test Page