Autor: John W. Baxter Data: A: Exim Mailing List Assumpte: Re: [exim] Problems sending to a server with call-out verification
On 5/28/06 2:06 AM, "Toralf Lund" <toralf@???> wrote:
> I've also tried telneting port 25 our server "from the outside", issuing
> the verification commands given in the Exim spec, and they seem to be
> successful. I'm wondering what the spec means by "the remote hosts",
> though. Does it contact the actual sending server, or the MX for the
> domain part of the address? Also, could it somehow be using a different
> port from 25?
Exim is trying to find out whether it could send a bounce message should the
need arise. It would send a bounce to the MX for the claimed sending
domain, so that's where the callback goes. And since a bounce would go to
port 25, no, it uses port 25. (All of the above assumes the absence of SRV
records in DNS...I don't know what happens in their presence.)
> Maybe 1.2.3.4 is a valid IP address, too...
As it happens, ARIN shows that 1.0.0.0/8 is "reserved". And if I were ever
assigned 1.2.3.0/24 for use, I'm pretty sure I wouldn't have a host at
1.2.3.4.
I'm a little sensitive to this, as we once got some strange packets coming
in to one of our IP addresses. It turned upon inquiry to the abuse person
at the sending site that the address had been used in an example in a rather
old IBM manual, and one of their machines had had the example copied in as
given. (Although we got the /24 containing the address in 1993, it's quite
possible that IBM owned the address when the manual was prepared.)
