RE: can't send to yahoo.com

From: <Paul_Lemonidis@xxxxxxxxxxx>
To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx>
Date: Wed, 11 Aug 2004 18:51:21 +0100

Hi Al

Apologies if I am teaching your grandmother to "suck eggs" in advance.

It is a goood way to reduce spam. Problem is that it tends to throw out "the
baby with dirty bath water".

What happens is that your ISP sets up a reverse look up record for your
server externally. A number of remote servers then use this and compare it
to the incoming source address. If they match fine. If not the message is
rejected as spam as it is assumed to have come from a spoofed address.

The problem with this is that I have seen valid business cases where this
scenario might actually be valid. In other words spoofing is done for quite
legitimate reasons. If you are going to say that strictly speaking the
server that is being spoofed legitimately should in fact allow relaying form
the address of the spoofer and make them send their messages properly I
totally agree. However, what business should do and what they actually do is
ultimately up to them I'm afraid.

Hope that helps?

Regards,

Paul Lemonidis.

----- Original Message ----- From: "Mulnick, Al" <Al.Mulnick@xxxxxxxxxx> To: "[ExchangeList]" <exchangelist@xxxxxxxxxxxxx> Sent: Wednesday, August 11, 2004 6:23 PM Subject: [exchangelist] RE: can't send to yahoo.com

http://www.MSExchange.org/

What would be the good reason?  Just out of curiosity.

-----Original Message-----
From: Lara, Greg [mailto:GLara@xxxxxxx]
Sent: Wednesday, August 11, 2004 1:08 PM
To: [ExchangeList]
Subject: [exchangelist] RE: can't send to yahoo.com

http://www.MSExchange.org/

I have to say that we have seen this problem with many exchange sites. A
lot
of admins (damn newbies) don't know to set their SMTP FQDN to the same as
their MX record in DNS, which is cause for an increasing number of ISPs to
reject mail, and for good reason.


Greg Lara
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-----Original Message-----
From: Rich Tibbets [mailto:rtibbets@xxxxxxxxxxxxxxxx]
Sent: Wednesday, August 11, 2004 12:50 PM
To: [ExchangeList]
Subject: [exchangelist] RE: can't send to yahoo.com

http://www.MSExchange.org/

Could you send the NDR, I just had a problem with my users not being able
to
send to AOL users.  It turned out to be DNS issue reverse DNS lookup
issue.
Once my ISP corrected this we could send to our AOL
clients again.

Rich Tibbets
-----Original Message-----
From: Lara, Greg [mailto:GLara@xxxxxxx]
Sent: Wednesday, August 11, 2004 11:55 AM
To: [ExchangeList]
Subject: [exchangelist] RE: can't send to yahoo.com

http://www.MSExchange.org/

Luke, is the NDR coming from your exchange server or from yahoo?


Greg Lara

-----Original Message-----
From: luke levis [mailto:luke.levis@xxxxxxxxxx]
Sent: Wednesday, August 11, 2004 11:47 AM
To: [ExchangeList]
Subject: [exchangelist] can't send to yahoo.com

http://www.MSExchange.org/

we recently upgraded our network to active directory and are running
windows
2003 server with Exchange server 2003 and for some reason now everytime
someone tries to send to and addres @yahoo.com they get and NDR, and in
our
previous environment we had no restrictions on who you could send it to..
and I am about 2 weeks into using E2k3 so I might as well have a blind
fold
on..


any help is appreciated

Luke


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RE: can't send to yahoo.com

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