Forcing sendmail to use /etc/hosts before using DNS

[Matt Kettler]

This is a result of SMTP standards requirements, some discussion can be
read here:

http://www.linuxgazette.com/issue31/tag_maildns.html

Really trying to deliver mail to a host without a valid MX record is a
somewhat dangerous thing to do as far as "accidental open relay" bugs are
concerned.

More info is easily found on google:

http://www.google.com/search?hl=en&ie=UTF-8&oe=UTF-8&q=sendmail+%2Fetc%2Fhosts&btnG=Google+Search

At 01:50 PM 1/13/2003 -0700, John B. Hanks wrote:
>I am trying to get sendmail/mailscanner to do something that has me
>questioning my understanding of the way this has been working. Here is what
>I currently do to scan mail for a mail server.
>
>My MailScanner machines are noturus.usu.edu and ameiurus.usu.edu.
>
>If I want to scan mail for mail.dept.usu.edu, I go to that DNS record and
>add
>
>mail.dept.usu.edu  in mx  10 noturus.usu.edu
>mail.dept.usu.edu  in mx  10 ameiurus.usu.edu
>
>This has been working flawlessly for some time. I think what happens is mail
>gets delivered to the MailScanner machines, they recognize themselves as MX
>hosts and then forward the scanned mail to the A record for the target.
>
>Now I need to do some magic for a server move. I have a host,
>someserver.usu.edu, that wants mail scanned and delivered to another box
>which will host mail but someserver.usu.edu still has other functions so it
>need to keep this name in its a record. I thought I could accomplish this by
>adding entries to /etc/hosts on the mailscanners like
>
>172.17.1.33      someserver.usu.edu
>
>So that when noturus or ameiurus looked up someserver.usu.edu they would use
>the entry from the hosts file and unwittingly deliver mail to the new
>server. But, sendmail seems intent on ignoring the /etc/hosts file. I have
>changed /etc/resolv.conf, /etc/nsswitch.conf, /etc/host.conf and
>/etc/mail/services.switch so that all these point to files first, then dns
>but it still isn't working. The ping command works as expected, checking
>/etc/hosts and using the IP address from the file. Can someone tell me if
>what I want to do is possible and if so, how do I get sendmail to behave
>this way? As we move more mailservers to use MailScanner this is going to
>come up again and I need a way to solve it.
>
>This is Redhat 7.3, MailScanner 4.11-1 and sendmail 8.11.6-15.
>
>Thanks,
>
>jbh