[Pkg-exim4-users] Problems concerning IPv6 Port 25's opening to the Internet

[Satoru Otsubo]

Hi,

I have some problems concerning IPv6 Port 25's opening to the Internet.

My PC: Linux squeeze Japanese version clean install.
 I use the normal exim4 package prepared by debian maintainers, that is, I did not compile exim4.
 This is server use, that is, no Grafical User Interface.
(Current kernel version: 2.6.32-5-686)

 My network is as follows:
  Internet-----ISP-----(dual connection)------Home Gate Way------(Lan)-----my PC

 My PC's IP address is a dynamic IP address assigned by ISP.
 The ISP provides both ipv4 and ipv6 addresses to my PC.
 My PC gets ipv6's dynamic IP address by RA (Router Advertisements) from HGW.
 
 (1) I examined whether Ipv6's tcp port 25 of my PC was open to the Internet,that is,
 I opened, by setting the HGW, ipv6's tcp port 25 of my PC to the Internet.
 I didn't filtered ipv6's tcp port 25 with ip6tables's settings of my PC.

 Using dpkg-reconfigure exim4-config,
 I set up /etc/exim4/update-exim4.conf.conf as smarthost type, as follows:

  dc_eximconfig_configtype='smarthost'
  dc_other_hostnames='........'
  dc_local_interfaces=''
  dc_readhost=''
  dc_minimaldns='false'
  dc_relay_nets='........'
  dc_smarthost='a.b.c.d::587'
  CFILEMODE='644'
  dc_use_split_config='false'
  dc_hide_mailname='false'
  dc_mailname_in_oh='true'
  dc_localdelivery='mail_spool'
  dc_relay_domains=''

 And I probed the open prots of my PC from outside the HGW as follows:

 $ nmap -6 -PN eeee:....:ffff
      (eeee:....:ffff is my PC's ipv6 address)

 But port 25 was shown as "filtered."

 (2) In comparison, I examined whether Ipv6's tcp port 22 (ssh) of my PC was open to the Internet, that is,
 I opened, by setting the HGW, ipv6's tcp port 22 of my PC to the Internet.
 I didn't filtered ipv6's tcp port 22 with ip6tables's settings of my PC.

 And I probed the open prots of my PC from outside the HGW as follows:

 $ nmap -6 -PN eeee:....:ffff
      (eeee:....:ffff is my PC's ipv6 address)

 And port 22 was shown as "open."

 I can't understand why Port 25 was shown as "filtered", although Port 22 was shown as "open."
 Why is Port 25 shown as "filtered" ?

 Thanks for any help

 Satoru