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justin_brody
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Joined: 26 Jan 2005
Posts: 283

PostPosted: Mon Oct 03, 2005 9:57 pm    Post subject: sendmail: host name lookup failure Reply with quote

Hi,
I'm trying to get sendmail going on my gentoo box. It seems to be doing fine delivering local mail, but delivering to outside addresses doesn't. It either gives me a host name lookup failure error; or it seems to try to relay through the localhost which doesn't work. Relevant lines of /var/mail/log:

Oct 3 17:51:12 sunya sendmail[28702]: j93LpCG7028702: Authentication-Warning: sunya.zero.
net: justin set sender to br@math.umd.edu using -f
Oct 3 17:51:12 sunya sendmail[28702]: j93LpCG7028702: from=br@math.umd.edu, size=64, c
lass=0, nrcpts=1, msgid=<200510032151.j93LpCG7028702@sunya.zero.net>, relay=justin@localho
st
Oct 3 17:51:12 sunya sm-mta[28708]: j93LpCSI028708: from=<br@math.umd.edu>, size=375,
class=0, nrcpts=1, msgid=<200510032151.j93LpCG7028702@sunya.zero.net>, proto=ESMTP, daemon
=MTA, relay=sunya.zero.net [127.0.0.1]
Oct 3 17:51:12 sunya sendmail[28707]: j93LpCG7028702: to=jdbr@gmail.com, delay=00:00:0
0, xdelay=00:00:00, mailer=relay, pri=120064, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, st
at=Sent (j93LpCSI028708 Message accepted for delivery)
Oct 3 17:51:52 sunya sm-mta[28710]: j93LpCSI028708: to=<jdbr@gmail.com>, delay=00:00:4
0, xdelay=00:00:40, mailer=relay, pri=120375, relay=smtp.comcast.net, dsn=4.0.0, stat=Defe
rred: Name server: smtp.comcast.net: host name lookup failure



Here's my sendmail.mc:
divert(-1)
divert(0)dnl
include(`/usr/share/sendmail-cf/m4/cf.m4')dnl
VERSIONID(`$Id: sendmail-procmail.mc,v 1.2 2004/12/07 01:59:31 g2boojum Exp $')d
nl
define('confDEF_USER_ID',"8:12")dnl
OSTYPE(`linux')dnl
DOMAIN(`generic')dnl
define(`SMART_HOST', `smtp.comcast.net')dnl
MASQUERADE_AS(comcast.net)dnl
FEATURE(`allmasquerade')dnl
FEATURE(`masquerade_envelope')dnl
define(`PROCMAIL_MAILER_PATH',`/usr/bin/procmail')dnl
FEATURE(`smrsh',`/usr/sbin/smrsh')dnl
FEATURE(`local_lmtp',`/usr/sbin/mail.local')dnl
FEATURE(`local_procmail')dnl
define(`PROCMAIL_MAILER_FLAGS',`procmail -Y -m $h $g $u')dnl
define(`PROCMAIL_MAILER_ARGS',`procmail -Y -m $h $g $u')dnl
DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl
MAILER(procmail)dnl
MAILER(local)dnl
MAILER(smtp)dnl
Cwlocalhost


And /etc/hosts:
127.0.0.1 sunya.zero.net sunya localhost


Don't really know what I'm doing - any help would be greatly appreciated!

Thanks,
Justin
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Pete M
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Joined: 30 Apr 2005
Posts: 154

PostPosted: Tue Oct 04, 2005 7:44 am    Post subject: Reply with quote

Justin

From your logs you seem to have a DNS issue
Quote:
Name server: smtp.comcast.net: host name lookup failure


Do you have valid nameserver entries in /etc/resolv.conf

To test your nameservers "emerge bind-tools" then on the command line as root try
Code:
# dig smtp.comcast.net

; <<>> DiG 9.2.5 <<>> smtp.comcast.net
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18492
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 3, ADDITIONAL: 0

;; QUESTION SECTION:
;smtp.comcast.net.              IN      A

;; ANSWER SECTION:
smtp.comcast.net.       900     IN      A       216.148.227.125
smtp.comcast.net.       900     IN      A       63.240.76.27
smtp.comcast.net.       900     IN      A       204.127.198.27
smtp.comcast.net.       900     IN      A       204.127.202.27

;; AUTHORITY SECTION:
comcast.net.            7200    IN      NS      dns01.jdc01.pa.comcast.net.
comcast.net.            7200    IN      NS      dns02.jdc01.pa.comcast.net.
comcast.net.            7200    IN      NS      adns.cmc.comcast.net.

;; Query time: 366 msec
;; SERVER: 192.168.0.3#53(192.168.0.3)
;; WHEN: Tue Oct  4 08:15:36 2005
;; MSG SIZE  rcvd: 170


This is the reply I get

Also as a side note to receive incoming mail you need to comment out this line
Code:
DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl


Make it like this
Code:
dnl # DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl


This makes sendmail listen on all interfaces not just your loopback

Pete
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justin_brody
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Joined: 26 Jan 2005
Posts: 283

PostPosted: Tue Oct 04, 2005 5:06 pm    Post subject: Reply with quote

Hi Pete,
Thanks for your response. Here's what I get from dig:
Code:

sunya justin # dig smtp.comcast.net

; <<>> DiG 9.2.5 <<>> smtp.comcast.net
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26447
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;smtp.comcast.net.              IN      A

;; ANSWER SECTION:
smtp.comcast.net.       566     IN      A       204.127.202.27
smtp.comcast.net.       566     IN      A       216.148.227.125
smtp.comcast.net.       566     IN      A       63.240.76.27
smtp.comcast.net.       566     IN      A       204.127.198.27

;; Query time: 39 msec
;; SERVER: 68.87.64.196#53(68.87.64.196)
;; WHEN: Tue Oct  4 12:57:00 2005
;; MSG SIZE  rcvd: 98


Which I gather is similar to what you have without the authority entires?

In case it helps, here's my resolv.conf
Code:
sunya justin # cat /etc/resolv.conf
nameserver 68.87.64.196
nameserver 68.87.66.196
nameserver 68.48.0.12
search hsd1.md.comcast.net.


(This is created via DHCP).

Poking around a bit, it looks like the MX record isn't working though:
Code:
sunya justin # nslookup
> set type=mx
> smtp.comcast.net
Server:         68.87.64.196
Address:        68.87.64.196#53

Non-authoritative answer:
*** Can't find smtp.comcast.net: No answer

Authoritative answers can be found from:
comcast.net
        origin = dns01.jdc01.pa.comcast.net
        mail addr = dnsadmin.comcast.net
        serial = 1348
        refresh = 900
        retry = 180
        expire = 604800
        minimum = 3600


Which seems strange, since my nameservers are from comcast. But then, I don't really know how this works. Is this a problem on their end?

For what it's worth, the same basic setup seemed to work fine a few weeks ago. I had a harddrive crash and had to reinstall GENTOO; but relaying through smtp.comcast.net did seem to work then...

Any ideas?
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justin_brody
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PostPosted: Tue Oct 04, 2005 6:17 pm    Post subject: Reply with quote

Well, I followed the example at http://davespicks.com/writing/programming/sendmailhostlookupfailure.html and this seems to work for me. Can anyone verify that the actualy problem is that Comcast doesn't have an MX entry for their own mail server???
-Justin
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Pete M
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PostPosted: Tue Oct 04, 2005 6:27 pm    Post subject: Reply with quote

Justin

Try it this way using square brackets this will prevent sendmail doing a MX lookup

Code:
define(`SMART_HOST', `[smtp.comcast.net]')dnl


Sendmail by default connects to port 25 and I have already tried

Code:
# telnet smtp.comcast.net 25


And it connects perfectly to comcasts mail server

Pete
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Pete M
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PostPosted: Tue Oct 04, 2005 6:30 pm    Post subject: Reply with quote

Sorry Justin

Did'nt read your post, been doing something else, glad you solved it

Pete
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