Somewhat OT email addresses

[Rick Stevens]

On Fri, 2006-02-17 at 12:54 +1100, Graeme Nichols wrote:
> Jeff Kinz wrote:
> > On Thu, Feb 16, 2006 at 01:29:32PM +1100, Graeme Nichols wrote:
> > 
> >>Hello Folks,
> >>
> >>I know this is somewhat OT but I was wondering if it is possible to send 
> >>an email with an address in the following format; username@[IP address]
> >>
> >>I have been fiddling around because a person with whom I was writing to 
> >>has suddenly become unknown, possibly because of DNS failure, I'm not 
> >>sure, and the mail is returned undeliverable as the domain is unknown. 
> >>They are having the same problem sending mail to me.
> >>
> >>I did a ping on my ISP's SMTP mail server and while there was a 100% 
> >>failure rate on the packets, most probably due to some firewall setting, 
> >>I was given the IP address, in this case, 203.12.160.34
> >>
> >>I sent a test email to name at 203.12.160.34 but it bounced with the 
> >>following error;
> > 
> > 
> > 
> > 
> > Graeme, I see one issue here that you would need to fix, assuming you
> > are trying to send am email to someone other than yourself.
> > 
> > You need to enter the IP address of their domain (or their domain's SMTP
> > server), not the IP of your ISP's SMTP server.
> > 
> > Or have I misunderstood your intent?
> > 
> > 
> Hi Jeff, You've understood me corectly. I made a few phone calls 
> yesterday and discovered that the people who own the domain have 
> apparently failed to renew it. Its no longer a valid domain name.
> 
> Before I discovered that I thought that there -may- have been a DNS 
> failure and it -may- have been possible to address the mail to their IP 
> address bypassing the DNS. I was sending mail from my account to the 
> address name@[my ISP's SMTP IP address], not their ISP's SMTP IP 
> address, which I cannot obtain anyway. My MTA sent the mail OK but it 
> bounced back with the error I posted earlier.

Outgoing mail should NEVER have your SMTP server's address in the name.
It must be the domain name of the recipient OR the IP address of the
recipient's MX server (as shown in a "dig domain.tld mx" command).  You
should NEVER specify your SMTP server in an address.  That's handled by
entries in your /etc/mail/sendmail.cf (or /etc/mail/client.cf) file.

> I haven't achieved my objective, for obvious reasons, but I have learned 
> a lot thanks to everyone who helped me. Who said you cannot teach an old 
> dog new tricks?
> 
> Thank you to everybody.
> 
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
-                                                                    -
-  Silence!  Or I shall replace you with a very small shell script!  -
-                                                - The Wizard of OS  -
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