VanLUG Email Archive
Alan Hodgson (ahodgson@simkin.com)
Sun, 28 Feb 1999 15:03:29 -0800
On Sun, Feb 28, 1999 at 10:07:34AM -0800, Ted Powell wrote:
> On Sun, Feb 28, 1999 at 12:10:05AM -0800, Randall Clark wrote:
> >
> > I am trying to use my mail server to send mail to islandnet.com and
> > victoria.tc.ca but they both come back with this error. You may have noticed
> > that I have ??? out the ip addresses and mail users names. anyone know what
> > is going on here??
> > [...]
> > >>><<< 418 <> > >>><<< 418 <viccam@24.64.???.???>... unresolvable host name
>
> With the amount of spamming going on on the net these days, mail sites
> generally will not accept mail from just anybody, without some idea of
> who they are.
>
> When your MTA (Mail Transport Agent) connects to islandnet.com (or
> victoria.tc.ca) it says, in effect, "Hi! I'm 24.64.111.222, and I'd like
> to lay some mail on you."
>
> Then islandnet.com does a DNS lookup on the name 24.64.111.222 to find
> out the corresponding IP address. Suppose for a moment that the lookup
> succeeds. It then takes the IP address that it got by looking up the
> provided host name, and compares it with the source IP address in the
> data packets you've sent it. If it doesn't match, then islandnet.com
> knows that you aren't who you say you are, and won't trust you.
>
Actually, it looks a little simpler than that - it looks like his
envelope sender is envelope sender is viccam@24.64.whatever. The receiving system is
just validating the domain portion of the envelope sender address,
not verifying the HELO information or reverse DNS.
I have no idea why the sending system would be trying to use I have no idea why the sending system would be trying to use user@ip_address
as an E-mail address, though.
-- Linux: because a PC is a terrible thing to waste
This archive was generated by hypermail 2.0b3 on Sun 28 Feb 1999 - 15:08:38 PST