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Date:      Mon, 15 Oct 2001 08:30:18 -0700
From:      "Brian" <bri@sonicboom.org>
To:        "Drew J. Weaver" <drew.weaver@thenap.com>, "'freebsd-net@freebsd.org'" <freebsd-net@FreeBSD.ORG>
Subject:   Re: DNS causing problems with sendmail?
Message-ID:  <007701c1558e$585a1460$3324200a@sonicboom.org>
References:  <B1A7D9973EBED3119ADD009027DC86492B16CF@MAILMAN>

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After the 2 or 3 minute delay, does it work?  Looked in /var/log/maillog =
for reject causes?  Are all the hosts you want to allow to send =
specified in /etc/mail/relay-domains?  If you want to try to see if dns =
is the cause, specify a few of the non working hosts in /etc/hosts.  =
Personally as an isp customer, if forward and reverse dns is not setup, =
I'd be looking for a new isp.  Some sites will not allow you to connect =
in this situation.  TCP wrappers often includes this entry.

# Prevent those with no reverse DNS from connecting.
ALL : PARANOID : RFC931 20 : deny

Bri
  ----- Original Message -----=20
  From: Drew J. Weaver=20
  To: 'freebsd-net@freebsd.org'=20
  Sent: Monday, October 15, 2001 5:40 AM
  Subject: DNS causing problems with sendmail?


  Hi, I've had this problem for a few days now, we have a small dial-up =
ISP and when users dial into one of our cities they get a =
209.xxx.xxx.xxx IP and our mail server responds normally, we have =
another modem pool in that city that consists of 206.xxx.xxx.xxx IP =
addresses, if a user gets a 206.xxx.xxx.xxx IP address and they attempt =
to check mail it takes a good 2-3 minutes before the sendmail connection =
starts, which is an obvious problem because of the timeouts on email =
clients (and.. 2-3 minutes is just bad). I've been kinda asking around =
on comp.mail.sendmail about this issue and they are telling me it is a =
DNS problem. Well, I know that my mail server can reverse the IP =
addresses because if I am logged in and issue a host command with the IP =
after it the server is able to produce the proper reverse name. Another =
user thought it was because I have no Forward dns (a record) for what =
the IPs are reversed to, but the fact is I've NEVER had any A records or =
anything for my modem pools. I also have another server running the same =
version of sendmail, and if I dial into this city and get a =
206.xxx.xxx.xxx IP and telnet to port 25 on that server it comes up =
instantly. So this appears to be an issue only effecting one daemon on =
one server. The afflicted server also runs a POP daemon that isn't =
having any problems of this type.

  =20

  Does anyone have a clue on this? I'm awfully confused at this point.

  =20

  Thanks,

  -Drew

  =20


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<DIV><FONT face=3DArial size=3D2>After the 2 or 3 minute delay, does it =
work?&nbsp;=20
Looked in /var/log/maillog for reject causes?&nbsp; Are all the hosts =
you want=20
to allow to send specified in /etc/mail/relay-domains?&nbsp; If you want =
to try=20
to see if dns is the cause, specify a few of the non working hosts in=20
/etc/hosts.&nbsp; Personally as an isp customer, if forward and reverse =
dns is=20
not setup, I'd be looking for a new isp.&nbsp; Some sites will not allow =
you to=20
connect in this situation.&nbsp; TCP wrappers often includes this=20
entry.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2># Prevent those with no reverse DNS =
from=20
connecting.<BR>ALL : PARANOID : RFC931 20 : deny<BR></FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Bri</DIV></FONT>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
  <DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
  <DIV=20
  style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
  <A title=3Ddrew.weaver@thenap.com =
href=3D"mailto:drew.weaver@thenap.com">Drew J.=20
  Weaver</A> </DIV>
  <DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Dfreebsd-net@FreeBSD.ORG=20
  =
href=3D"mailto:'freebsd-net@freebsd.org'">'freebsd-net@freebsd.org'</A> =
</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Monday, October 15, 2001 =
5:40=20
  AM</DIV>
  <DIV style=3D"FONT: 10pt arial"><B>Subject:</B> DNS causing problems =
with=20
  sendmail?</DIV>
  <DIV><BR></DIV>
  <DIV class=3DSection1>
  <P class=3DMsoNormal style=3D"TEXT-INDENT: 0.5in"><FONT face=3DArial =
size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Hi, I've had this =
problem for a=20
  few days now, we have a small dial-up ISP and when users dial into one =
of our=20
  cities they get a 209.xxx.xxx.xxx IP and our mail server responds =
normally, we=20
  have another modem pool in that city that consists of 206.xxx.xxx.xxx =
IP=20
  addresses, if a user gets a 206.xxx.xxx.xxx IP address and they =
attempt to=20
  check mail it takes a good 2-3 minutes before the <SPAN=20
  class=3DSpellE>sendmail</SPAN> connection starts, which is an obvious =
problem=20
  because of the timeouts on email clients (and.. 2-3 minutes is just =
bad). I've=20
  been <SPAN class=3DSpellE>kinda</SPAN> asking around on <SPAN=20
  class=3DSpellE>comp.mail.sendmail</SPAN> about this issue and they are =
telling=20
  me it is a DNS problem. Well, I know that my mail server can reverse =
the IP=20
  addresses because if I am logged in and issue a host command with the =
IP after=20
  it the server is able to produce the proper reverse name. Another user =
thought=20
  it was because I have no Forward <SPAN class=3DSpellE>dns</SPAN> (a =
record) for=20
  what the <SPAN class=3DSpellE>IPs</SPAN> are reversed to, but the fact =
is I've=20
  NEVER had any <SPAN class=3DGramE>A</SPAN> records or anything for my =
modem=20
  pools. I also have another server running the same version of <SPAN=20
  class=3DSpellE>sendmail</SPAN>, and if I dial into this city and get a =

  206.xxx.xxx.xxx IP and telnet to port 25 on that server it comes up =
instantly.=20
  So this appears to be an issue only effecting one daemon on one =
server. The=20
  afflicted server also runs a POP daemon that isn't having any problems =
of this=20
  type.<o:p></o:p></SPAN></FONT></P>
  <P class=3DMsoNormal style=3D"TEXT-INDENT: 0.5in"><FONT face=3DArial =
size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
  <P class=3DMsoNormal style=3D"TEXT-INDENT: 0.5in"><FONT face=3DArial =
size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: Arial">Does anyone have a clue =
on this?=20
  I'm awfully confused at this point.<o:p></o:p></SPAN></FONT></P>
  <P class=3DMsoNormal style=3D"TEXT-INDENT: 0.5in"><FONT face=3DArial =
size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P>
  <P class=3DMsoNormal style=3D"TEXT-INDENT: 0.5in"><FONT face=3DArial =
size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Arial">Thanks,<o:p></o:p></SPAN></FONT></P>
  <P class=3DMsoNormal style=3D"TEXT-INDENT: 0.5in"><FONT face=3DArial =
size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Arial">-Drew<o:p></o:p></SPAN></FONT></P>
  <P class=3DMsoNormal style=3D"TEXT-INDENT: 0.5in"><FONT face=3DArial =
size=3D2><SPAN=20
  style=3D"FONT-SIZE: 10pt; FONT-FAMILY: =
Arial"><o:p>&nbsp;</o:p></SPAN></FONT></P></DIV></BLOCKQUOTE></BODY></HTM=
L>

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