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Spam in the same domain

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Spam in the same domain - 25.Jan.2008 9:01:59 AM

olandese

Posts: 3
Joined: 25.Jan.2008
Status: offline

Hello,

i have a Exchange 2007 installation, just one server, and this server hangs on the internet. (port 25 is forwarded from my router to the server)

The Receive Connector accepts anonymous emails.
In The accepted domains i accept only my domain name.
I made an Internet send connector.

Everythings works fine, i can send email to external domains, i can receive email from external domains.

The problem is that i'm able to anonymous login in telnet to my exchange server and send emails to everybody in my domain.
Example: from spam@thisismydomain.com to user@thisismydomain.com
or user@thisismydomain.com to user@thisismydomain.com.

Fortunately it is not possible to send in the same way email to other external domains (open relay).

Who can help me?

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RE: Spam in the same domain - 25.Jan.2008 11:25:56 AM

John Weber

Posts: 1236
Joined: 20.Apr.2005
From: Portland, Oregon
Status: offline

I am not sure I understand what the problem is.
If you don't have it setup this way, how are you going to receive email from someone you don't know?

You don't have an open relay, yet you can accept mail from unknowns - perfect.

Are you trying to set the system up to only allow email from particular hosts?

_____________________________

John Weber [Lync MVP] http://tsoorad.blogspot.com

(in reply to olandese)

Post #: 2

RE: Spam in the same domain - 25.Jan.2008 4:26:47 PM

olandese

Posts: 3
Joined: 25.Jan.2008
Status: offline

the problem is that everybody from the internet is able to enter in my server and send email as a user of my domain to other users of my domain. (like spam, but only in my domain)

Example:

somebody enters via telnet port 25 to my smtp server, then this one is able to send email from spamuser@mydomain.com to user@mydomain.com.

(in reply to John Weber)

Post #: 3

RE: Spam in the same domain - 29.Jan.2008 5:44:55 AM

rishishah

Posts: 784
Joined: 14.Nov.2006
From: Surrey, UK
Status: offline

"the problem is that everybody from the internet is able to enter in my server and send email as a user of my domain to other users of my domain. (like spam, but only in my domain)"

This is standard e-mail delivery....everybody on the internet being able to send mail to your domain...

When you use the telnet port 25 to a mailsever, this allows you to send a standard SMTP message and is not spam.

_____________________________

Rishi Shah, MCP

Remember to backup before applying the advice. www.saiconsult.co.uk. Happy to provide Professional Exchange Server Consultancy to anywhere in the world.

(in reply to olandese)

Post #: 4

RE: Spam in the same domain - 29.Jan.2008 8:49:01 AM

olandese

Posts: 3
Joined: 25.Jan.2008
Status: offline

Ok, maybe i didn't explain it good but let's say for example that my email is olandese@mydomain.com.

I'm receiving mails from somebody as olandese@mydomain.com, how is this possible?

I was looking if this could be done through my smtp (exchange 2007) server, and yes!

It's like somebody is sending email to users in my domain as a user of my domain, even if the from mailbox doens't exist.

Example:
In my domain i have only 2 mailboxes:
user1@mydomain.com
user2@mydomain.com

user1@mydomain.com (or user2) is getting emails from user3@mydomain.com even it doensn't exist.

I was thinking, is this done through my smtp server?
I tried to do this scenario telnetting my smpt server from the internet, and indeed it was possible.
My question is, how can i avoid this?

I was not able to send emails as user3@mydomain.com to external domains, so this is configured good.

(in reply to rishishah)

Post #: 5

RE: Spam in the same domain - 30.Jan.2008 5:58:49 AM

rishishah

Posts: 784
Joined: 14.Nov.2006
From: Surrey, UK
Status: offline

All you need to do than is to block any mail comming at your gateway SMTP server with your domain as the Sender.

You can do this with TRansport rules on the Edge or via any other suitable Anti-spam appliance/software on your gateway SMTP.

_____________________________

Rishi Shah, MCP

Remember to backup before applying the advice. www.saiconsult.co.uk. Happy to provide Professional Exchange Server Consultancy to anywhere in the world.

(in reply to olandese)

Post #: 6