Comcast and mail header errors?

[Bruce Dawson]

Ben Scott wrote:
> On 3/21/06, Paul Lussier <p.lussier at comcast.net> wrote:
>>  Received: from linux.codemeta.com (pm.codemeta.com[199.125.76.1](misconfigured sender)
> 
> $ host linux.codemeta.com
> linux.codemeta.com has address 199.125.76.10
> $ host pm.codemeta.com
> pm.codemeta.com has address 199.125.76.1
> $ host 199.125.76.1
> 1.76.125.199.in-addr.arpa domain name pointer pm.codemeta.com.
> $
> 
>   I'm still guessing here, but my guess is: When the sender-SMTP
> connects to Comcast, it is HELO'ing as "linux.codemeta.com".  DNS says
> linux.codemeta.com has IP address 199.125.76.10.  However, the
> sender-SMTP is at IP address 199.125.76.1.  Thus, "misconfigured
> sender" -- the sender-SMTP is claiming to be one system, but DNS does
> not agree.
> 
>   This could occur legitimately in a system with multiple IP addresses.

Hmmm. What does linux.codemeta.com or pm.codemeta.com have to do with
gnhlug.org's email? Or does this thread have some barn-sized holes in
it? Or is someone just using this as an example?

pm.codemeta.com and linux.codemeta.com are on the same computer. One is
a point-to-point connection to the outside world; the entry point to a
firewall. The other is within the firewall (or at least should be).

Connections to a remote system may have a "source address" as
199.125.76.1 (and if things on 199.125.76.10 are bound to the right
source address, they shouldn't), but there should be no way to connect
back to that IP address - you have to use the name in the header (which
should be linux.codemeta.com).

If there are any questions about the configuration of that system,
please send them to me off-list.

--Bruce