XPost: comp.unix.bsd.freebsd.misc, comp.unix.programmer   
   From: lesen@wimezu.com   
      
   Winston  writes:   
      
   > Lesley Esen  writes:   
   >> # tcpdump -n port 25   
   >> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode   
   >> listening on ena0, link-type EN10MB (Ethernet), capture size 262144 bytes   
   >> 09:01:45.939473 IP 172.26.5.226.37963 > 69.164.210.174.25: Flags   
   >> [S], seq 1665376094, win 65535,   
   >   
   > 172.26.*.* is private, not public, IP address space.  If that's the TCP   
   > source address being sent to the remote hosts, it's not surprising   
   > you're not getting an answer.  If I'm reading your article right, the   
   > public IP address 34.197.192.71.   
      
   That's the public IP address, yes.  This is typical on the AWS network.   
   Each instance gets a private and a public IP address.  I never see the   
   public IP address in the instance, but the packets must be being   
   rewritten by the AWS network because I can communicate with the outside   
   world just fine.   
      
   > If you can't solve the problem directly, you may need to relay outbound   
   > mail via some AWS mail forwarder, if they have them.   
      
   I think that's also possible.   
      
   >> The host 69.164.210.174 also runs an SMTP server, but someone seems to   
   >> block my path to it.  It might not AWS as I also can't reach it from my   
   >> personal computer (with a dynamic IP address).   
   >   
   > Try "netstat -an4" on 69.164.210.174 to verify that the mail server is   
   > indeed listening on port 25.   
      
   %netstat -an4 | grep 25   
   tcp        0      0 0.0.0.0:25              0.0.0.0:*               LISTEN   
   tcp        0      0 69.164.210.174:25       194.169.175.47:34740    TIME_WAIT   
   tcp        0      0 69.164.210.174:25       194.169.175.47:40116    TIME_WAIT   
      
   Thanks!   
      
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