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Re: help!! relay host!!



Hello bhasker,
"Relay"ing in sendmails context is what happens when an MTA (like
sendmail running as an local smtp daemon) is asked to transfer or
handle a mail that is not from or destined to a user this MTA is in.

For example, you are sending mail to your friend at yahoo - 
	willie@xxxxxxxxx

You are in IIT and your address would be - 
	bhasker@xxxxxxxxxxxxx

If now the mail server at hclt.com was asked to deliver this mail, it
is being asked to relay.

Now you wonder what you did wrong? The problem probably is that you
seem to have set your address in your MUA (probably netscape/pine) to
some hotmail.com account and since neither the sender nor the
recepient belong to the MTAs domain (something.iitm.ernet.in), it
refuses to relay.

Now why is relaying such a big deal? Because it used to be the
largest vehicle for spam. People would forge addresses and send mail
by connecting to some arbitrary SMTP server on the Net and using
unqualified user names.

So for example at college we used to connect to beetle.mot.com
(motorola) and send mails stating the address in the "Mail from"
field to be just "veliath". The mails would show up as coming from
"veliath@xxxxxxxxxxxxxx"!

When sysadms woke up to this the first thing they did was to not
accept for delivery mails that had unqualified user names and to not
do relaying.

These are the default settings in all MTAs now.

Ycan turn it off by specifying "promiscuous relaying" in your
sendmail file.  The best thing to do would be to download the
sendmail source distribution from sendmail.org and read the file on
configuration of sendmail in sendmail-8.9.2/cf/README.

Ycan enable relaying to various degrees, but I doubt I can really
tell you all of it in a mail. So its best yread the README.

BTW for my project team I maintain the MX server and we hit this
problem because our server sits on 3 domains and it wouldn't relay
mails between them without us twisting its arms into doing it.
basically our users were on one domain, our test machines on another
and our clients on the third.

Hope the above helps and if yknow all this already, I am sorry.

veliath

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