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SpamFilter ISP Creats OPEN RELAY????!!!

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chinabee View Drop Down
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    Posted: 08 September 2003 at 12:04pm

Just found this out. Anybody can use the SpamFilter ISP as a reply to send emails to anybody in my domain. Of course, I did this from outside of my network. I didn't have to fake FROM address. I can use abc@yahoo.com and send emails to anybody in my domain.

Of course, I can't really send email to anybody outside of my domain.

HELP!!!

OPEN RELAY TEST

Connecting to 61.46.23.174 for anonymous test ...

<<< 220 mail.mycompany.com  Welcome to LogSat's Software ESMTP Server v1.2.0.178>>> HELO http://www.abuse.net
<<< 250 Hello http://www.abuse.net

Relay test 1

>>> RSET
<<< 250 Ok
>>> MAIL FROM:<spamtest@abuse.net>
<<< 250 spamtest@abuse.net Address Okay
>>> RCPT TO:<relaytest@abuse.net>
<<< 250 relaytest@abuse.net Address Okay

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LogSat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LogSat Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2003 at 1:13pm

SpamFilter is supposed to allow anyone on the outside send emails to your internal users. If it weren't like that, nobody would ever be able to send you email...

The problem would be if external users were able to use your server to then bounce (send) email to servers other than yours. That would mean you are an open relay. But if they are simply sending email to your users, that is absolutely not being an open relay, it is simply how email works.

Roberto F.
LogSat Software

====

Just found this out. Anybody can use the SpamFilter ISP as a reply to send emails to anybody in my domain. Of course, I did this from outside of my network. I didn't have to fake FROM address. I can use abc@yahoo.com and send emails to anybody in my domain.

>

Of course, I can't really send email to anybody outside of my domain.

HELP!!!

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chinabee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote chinabee Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2003 at 1:20pm
That means anybody can use my IP as their outgoing SMTP server and send emails to me?
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LogSat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LogSat Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2003 at 1:36pm

Absoutely. If it weren't so, the other SMTP servers would never be able to send you emails... Email clients and SMTP servers "talk" the same way to your incoming SMTP server (the one you MX record points to). If they were not able to send your users emails then you would never receive anything...

Roberto F.
LogSat Software

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That means anybody can use my IP as their outgoing SMTP server and send emails to me?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote chinabee Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2003 at 2:24pm

I kind of understand this now.

How can I prevent others from SPAM me then? Can people just use my SMTP server as their Outgoing SMTP server and start spamming me?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote BillStewart Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2003 at 3:35pm

Maybe I don't understand your question, but that's why you'd invest in a product such as SpamFilter -- it's an SMTP server with spam filtering features designed to help eliminate spam.

Secondly, I think you need some basic understanding of how SMTP works before you start posting more questions.

HTH,

Bill

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Post Options Post Options   Thanks (0) Thanks(0)   Quote George Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2003 at 10:30pm

First off your outgoing smtp server should have the ability to allow and block senders using a local black/white list ie "allowed relays/ blocked senders". If you only allow ip's  that you want to relay through you then that will prevent unwanted users from using your smtp server as an open relay.

Secondly, SpamFilter ISP should only be used to accept all incomming email. It will then forward all filtered emails to your pop/smtp server. People should not be able to use the SpamFilter ISP server as an outgoing smtp server.

 

George

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Post Options Post Options   Thanks (0) Thanks(0)   Quote LogSat Quote  Post ReplyReply Direct Link To This Post Posted: 08 September 2003 at 11:19pm

Just as the name implies, that's what SpamFilter for ISP is used for!

Roberto F.
LogSat Software

 

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eric View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote eric Quote  Post ReplyReply Direct Link To This Post Posted: 14 September 2003 at 12:11pm

ROTFL...

we had a security officer stating the same...

telnet to any isp,

rcpt to: postmaster@RDNSNAME.FQDN

and guess what, they accept mail, isn`t it wonderfull ?

it is smtp !

-eric-

// kind people say ehlo first before flaming in the forum.. //

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