GEN:SID 1:654
Message SMTP RCPT TO overflow
Summary When connecting to port 25 (SMTP) on a computer running a vunarable SMTP server it is possible to perform a DoS attack. In some cases it might be possible to perform a security breach as well.
Impact Depending on the vunerable software you may need to restart the SMTP server or perform some level of incident response.
Detailed Information Vulnerable systems:
    Avirt Mail 4.0 (build 4124)
    Avirt Mail 4.2 (build 4807)
    PakMail SMTP/POP3
    Netscape Messaging Server 3.54/3.55/3.6

More details can be found on the various sites listed below as the impact and details vary from system to system.
Affected Systems  
Attack Scenarios Supply a large amount of data after the RCPT TO: header in your SMTP flow.
Ease of Attack DoS: rather easy
Security breach: probably hard
Corrective Action Upgrade software according to the instructions of your software manufacturer.
Additional References http://www.securiteam.com/exploits/6C00O1F00Y.html
http://www.synnergy.net/downloads/advisories/SLA-2000-01.pakmail.txt
http://online.securityfocus.com/bid/748
Rule References bugtraq: 2283
bugtraq: 9696
cve: 2001-0260