SMTP service on Cisco VPN Concentrator

Hi,
I was carrying out a pen-test on a Cisco VPN Concentrator (3000),
nessus 3.0 scan discovered a number of mail-related ports such as SMTP
at 988, imaps at 993 and https at 443.  I try to telnet to the port
988 to verify but cannot get anything even a banner.

Initially i considered this as false positive, but after some search
on google,  it seems Cisco VPN Concentrator do has some smtp proxy at
port 988 and imaps services.   I cannot find any other traces of these
smtp ports besides the nessus report.

Is there anyone has more information on these smtp proxy services on
Cisco VPN concentrator (3000)? Any known security issues with these
services on? Thanks.

regards,
Rick Zhong

www.sinfosec.org
www.security.org.sg

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