Fortinet » Fortinet28 : Security Vulnerabilities, CVEs,

An unspecified Fortinet product, possibly Fortinet28, allows remote attackers to cause a denial of service via a "small synflood" to the SMTP port (TCP port 25), as demonstrated by a 10-microsecond wait between sending packets. NOTE: this issue has been disputed in followup posts that suggest that a protection feature is triggering a RST.