Very Computer

by **Graham Dicke** » Thu, 04 May 2000 04:00:00

Hi to all

I have installed Red Hat Linux on a machine that is on a LAN to which an
IBM RS6000 is also connected. I can send mail from the RS6000 to the
Linux box OK but it doesn't work in the other direction. Any attempt to
send mail from Linux to RS6000 gets queued with the reason "host name
lookup failure".
I have a big fat sendmail manual but it doesn't mention this kind of
error explicitly and I'm a novice with Linux. Myself and a colleague
who has a good deal of experience with Unix have been hacking at the
hosts file and sendmail.cf (mostly via linuxconf) for a week now
with no luck.

The basic info is:

Red Hat Linux release 6.1 (Cartman)
Kernel 2.2.12-20

Sendmail Version 8.9.3
Compiled with LOG MATCHGECOS MIME7TO8 MIME8TO7NAMED_BIND NETINET
NETUNIX NEWDB NIS QUEUE SCANF SMTP USERDB

short domain name $w = ourmail
canonical domain name $j = ourmail.mycompany.co.uk
subdomain name $m = mycompany.co.uk
node name $k = ourmail.mycompany.co.uk

The /etc/hosts file contains

128.0.0.9 ourmail.mycompany.co.uk ourmail linux
128.0.0.10 theibm.mycompany.co.uk theibm
127.0.0.1 localhost

I can telnet onto the IBM from the Linux machine - so why can't I send
mail? What does "host name lookup failure" mean anyway?

TIA
--

by **Michael Elizaro** » Thu, 04 May 2000 04:00:00

> Hi to all

> I have installed Red Hat Linux on a machine that is on a LAN to which an
> IBM RS6000 is also connected. I can send mail from the RS6000 to the
> Linux box OK but it doesn't work in the other direction. Any attempt to
> send mail from Linux to RS6000 gets queued with the reason "host name
> lookup failure".

You should check your DNS configuration first. As a simple solution (you
have only two boxes, right?) make sure /etc/hosts files look similar. And
that you have a line
order hosts,bind
in your resolv.conf.

Quote:
> I have a big fat sendmail manual but it doesn't mention this kind of
> error explicitly and I'm a novice with Linux. Myself and a colleague
> who has a good deal of experience with Unix have been hacking at the
> hosts file and sendmail.cf (mostly via linuxconf) for a week now
> with no luck.

> The basic info is:

> Red Hat Linux release 6.1 (Cartman)
> Kernel 2.2.12-20

> Sendmail Version 8.9.3
> Compiled with LOG MATCHGECOS MIME7TO8 MIME8TO7NAMED_BIND NETINET
> NETUNIX NEWDB NIS QUEUE SCANF SMTP USERDB

> short domain name $w = ourmail
> canonical domain name $j = ourmail.mycompany.co.uk
> subdomain name $m = mycompany.co.uk
> node name $k = ourmail.mycompany.co.uk

> The /etc/hosts file contains

> 128.0.0.9 ourmail.mycompany.co.uk ourmail linux
> 128.0.0.10 theibm.mycompany.co.uk theibm
> 127.0.0.1 localhost

> I can telnet onto the IBM from the Linux machine - so why can't I send
> mail? What does "host name lookup failure" mean anyway?

Do you telnet using name or dotted notation? In the first case make sure you
do not have junk in aliases file, in the second it's DNS. Get "DNS and BIND"
and read it.

- Show quoted text -

> TIA
> --

by **Graham Dicke** » Fri, 05 May 2000 04:00:00

>> Hi to all

>> I have installed Red Hat Linux on a machine that is on a LAN to which an
>> IBM RS6000 is also connected. I can send mail from the RS6000 to the
>> Linux box OK but it doesn't work in the other direction. Any attempt to
>> send mail from Linux to RS6000 gets queued with the reason "host name
>> lookup failure".

>You should check your DNS configuration first. As a simple solution (you
>have only two boxes, right?) make sure /etc/hosts files look similar. And
>that you have a line
> order hosts,bind
>in your resolv.conf.

I think we ticked the option in linuxconf to not use DNS. Maybe that
doesn't work?
There are lots of computers on the LAN and eventually we will want to do
some more sophisticated things with mail but at the moment we are
working with just two machines.
The host files are very similar.
I'll check resolv.conf today.

- Show quoted text -

Quote:
>> I have a big fat sendmail manual but it doesn't mention this kind of
>> error explicitly and I'm a novice with Linux. Myself and a colleague
>> who has a good deal of experience with Unix have been hacking at the
>> hosts file and sendmail.cf (mostly via linuxconf) for a week now
>> with no luck.

>> The basic info is:

>> Red Hat Linux release 6.1 (Cartman)
>> Kernel 2.2.12-20

>> Sendmail Version 8.9.3
>> Compiled with LOG MATCHGECOS MIME7TO8 MIME8TO7NAMED_BIND NETINET
>> NETUNIX NEWDB NIS QUEUE SCANF SMTP USERDB

>> short domain name $w = ourmail
>> canonical domain name $j = ourmail.mycompany.co.uk
>> subdomain name $m = mycompany.co.uk
>> node name $k = ourmail.mycompany.co.uk

>> The /etc/hosts file contains

>> 128.0.0.9 ourmail.mycompany.co.uk ourmail linux
>> 128.0.0.10 theibm.mycompany.co.uk theibm
>> 127.0.0.1 localhost

>> I can telnet onto the IBM from the Linux machine - so why can't I send
>> mail? What does "host name lookup failure" mean anyway?

>Do you telnet using name or dotted notation? In the first case make sure you
>do not have junk in aliases file, in the second it's DNS. Get "DNS and BIND"
>and read it.

We use the name "theibm". I'll check the aliases file and order the
book.

Many thanks

--

by **Michael Elizaro** » Fri, 05 May 2000 04:00:00

> I think we ticked the option in linuxconf to not use DNS. Maybe that
> doesn't work?

Oops... Have never used linuxconf and have heard a lot about it. As a sidebar:
IMHO you should either do all configuration manually editing files, or use a tool
(linuxconf). Do not do both, it's too easy to*up (from personal
experience:).
Can you clarify a bit about "option in linuxconf to not use DNS"?

Quote:
> There are lots of computers on the LAN and eventually we will want to do
> some more sophisticated things with mail but at the moment we are
> working with just two machines.

IMHO up to ten hosts are fine with hosts file being copied back and forth. For
more you'd better set up DNS.

Quote:
> We use the name "theibm". I'll check the aliases file and order the
> book.

BTW, there are a set of perl scripts for configuring sendmail. You will not even
need to understand m4. Unfortunately, I do not remember the package name (hey,
guys, who do?), *you should be able to find it on the freshmeat.

-- Mike

by **Graham Dicke** » Sun, 07 May 2000 04:00:00

>> I think we ticked the option in linuxconf to not use DNS. Maybe that
>> doesn't work?

>Oops... Have never used linuxconf and have heard a lot about it. As a sidebar:
>IMHO you should either do all configuration manually editing files, or use a
>tool
>(linuxconf). Do not do both, it's too easy to*up (from personal
>experience:).

I agree - I use only linuxconf to configure the real sendmail.cf but I
also run many tests with a purely hand-coded version.

Quote:>Can you clarify a bit about "option in linuxconf to not use DNS"?

There is a check box "do not use DNS". Checking/unchecking it makes
significant (and complex) changes to sendmail.cf. I have always left it
checked.

Quote:
>> There are lots of computers on the LAN and eventually we will want to do
>> some more sophisticated things with mail but at the moment we are
>> working with just two machines.

>IMHO up to ten hosts are fine with hosts file being copied back and forth. For
>more you'd better set up DNS.

All the machines on the LAN are Windows except the Linux box and the
RS6000. All the Windows machines use DHCP. If I must have a DNS server
too (and I have no reason why I shouldn't have one) its going to be the
Linux box anyway.

Quote:
>> We use the name "theibm". I'll check the aliases file and order the
>> book.

>BTW, there are a set of perl scripts for configuring sendmail. You will not even
>need to understand m4. Unfortunately, I do not remember the package name (hey,
>guys, who do?), *you should be able to find it on the freshmeat.

Yesterday I installed the sendmail source and spent some time reading
it. The mysterious "host name lookup failure" message is a sendmail
message. Its tough to figure out why it happens but my best guess is
that its a response by sendmail to an error return from the mailer
program. What I can't see from the debug output is what program is being
used as the mailer. I also speculate that maybe the Linux box is trying
to use ESMTP but the crusty old IBM only understands SMTP. I am thinking
of running sendmail under a de* but I don't know what kind of
debugging facilities are available to me. Or I could just stick some
diagnostic messages into sendmail and recompile it. I'd appreciate some
advice from wiser heads on this kind of approach.

Am I right in thinking that if sendmail decides to use SMTP to deliver
the mail then there is no separate executable for this i.e. the SMTP
mailer is built into sendmail itself?

Thanks

--

by **Duncan Simps** » Tue, 09 May 2000 04:00:00

Quote:>Yesterday I installed the sendmail source and spent some time reading
>it. The mysterious "host name lookup failure" message is a sendmail
>message. Its tough to figure out why it happens but my best guess is
>that its a response by sendmail to an error return from the mailer
>program.

Nope, this message is generated by sendmail attempting to look up a
host and failing. You have a DNS problem. Possible causes include:
1. Failure to specify remsmtp (or equivilently marking all SMTP mailers
as expensive and setting the HoldExpensive option) with a non-permanent
vonnection.

2. Broken DNS configuration
3. Sending mail to broken sites wiht no MX or A records. (*.ac.kr for
some open spam rely values of * comes to mind).
<rest of message also snipped>

Sendmail can cope with things that only understand SMTP correctly,
unless they violate the spec, for example by disconnection when one
says EHLO to them. ESMTP is spoken almost everywhere and includes
SMTP, so anything that just talks SMTP has no problems. SMTP and ESMTP
mailers are built into sendmail, no external mailer porgam is being
invoked.

A DNS server is *very strongly recommeneded*, epsecially for windows
clients (which always want to ask one before refering a to a hosts
file). Setting one up will also make double reverse DNS using beasts
happier and avoid the needed to update 29000 hosts files when a new
box appears.

Given the information exactly what your problem(s) are is hard to know.

--
Duncan (-:
"software industry, the: unique industry where selling substandard goods is
legal and you can charge extra for fixing the problems."

by **Graham Dicke** » Tue, 09 May 2000 04:00:00

Quote:
>>Yesterday I installed the sendmail source and spent some time reading
>>it. The mysterious "host name lookup failure" message is a sendmail
>>message. Its tough to figure out why it happens but my best guess is
>>that its a response by sendmail to an error return from the mailer
>>program.

>Nope, this message is generated by sendmail attempting to look up a
>host and failing. You have a DNS problem. Possible causes include:
> 1. Failure to specify remsmtp (or equivilently marking all SMTP mailers
> as expensive and setting the HoldExpensive option) with a non-permanent
> vonnection.

> 2. Broken DNS configuration
> 3. Sending mail to broken sites wiht no MX or A records. (*.ac.kr for
> some open spam rely values of * comes to mind).
><rest of message also snipped>

I also get exactly the same failure even when I specify the IP address
explicitly e.g.

would that still be consistent with a DNS problem? Jeez I wish I knew
more about DNS! Are you saying that the "do not use DNS" checkbox is not
doing what it says?

Quote:>Sendmail can cope with things that only understand SMTP correctly,
>unless they violate the spec, for example by disconnection when one
>says EHLO to them. ESMTP is spoken almost everywhere and includes
>SMTP, so anything that just talks SMTP has no problems. SMTP and ESMTP
>mailers are built into sendmail, no external mailer porgam is being
>invoked.

Understood. If I can I will run sendmail under a de* and trace the
exact path of execution.

Quote:>A DNS server is *very strongly recommeneded*, epsecially for windows
>clients (which always want to ask one before refering a to a hosts
>file). Setting one up will also make double reverse DNS using beasts
>happier and avoid the needed to update 29000 hosts files when a new
>box appears.

I think I will try making the Linux box be a DNS server too. I will
study the manuals to see how to do this over the next few days.
Presumably there is a way to co-ordinate this with the NT machine that
is currently doing DHCP for the Windows users? Or can Linux use DHCP
too? Uurrgghh...No! No! This is fun! No really!

Many thanks

--

Very Computer

help with sendmail please

help with sendmail please

help with sendmail please

help with sendmail please

help with sendmail please

help with sendmail please

help with sendmail please

help with sendmail please