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Spamming???

Posted on 2006-06-26
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Last Modified: 2010-03-06
I have turned up the logging on my SMTP Service and i see a lot of this...

This is an SMTP protocol error log for virtual server ID 1, connection #45560. The remote host "216.159.242.70", responded to the SMTP command "rcpt" with "550 5.1.1 User unknown  ". The full command sent was "RCPT TO:<saoyocxq@boelter-yates.com>  ".  This will probably cause the connection to fail.

Are people spamming through me?

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Question by:eenlow
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Expert Comment

by:Exchgen
ID: 16987124
You are right.....

If you find too many of the above events being generated, its an indication that someone is trying to harvest your address book to get names and email address of all valid users in your organization.

Please followup steps mentioned in the articles below to secure your environment;

How to prevent unsolicited commercial e-mail in Exchange 2003
http://support.microsoft.com/?kbid=821746

How to configure connection filtering to use Realtime Block Lists (RBLs) and how to configure recipient filtering in Exchange 2003
http://support.microsoft.com/?kbid=823866

TechNet Support WebCast: Fighting spam using Microsoft Exchange Server 2003
http://support.microsoft.com/?kbid=841058

A software update is available to help prevent the enumeration of Exchange Server 2003 e-mail addresses
http://support.microsoft.com/?kbid=899492

Please do consider using the software update to prevent email address harvesting.

Raghu
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Expert Comment

by:december41991
ID: 16987144
Cause: Recipient Filtering had been enabled for "recipients not in the directory"

No one is spamming you :) atleast thats what I think.
If you really want to check try sending a mail to your self by telnet usung bogus email as sender.


Recipient Filtering
http://support.microsoft.com/default.aspx?scid=kb;en-us;823866


Regards
Dominic
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december41991 earned 500 total points
ID: 16987157
actually people are trying to but not able to:

4. Exchange Server determines whether the Filter recipients who are not in the Directory check box is selected on the Recipient Filtering tab of the Message Delivery Properties dialog box. If this check box is selected, and if the recipient does not appear in the Active Directory directory service, Exchange Server returns the following error message to the sender:
550 5.1.1 User unknown
 

Source:
Recipient Filtering
http://support.microsoft.com/default.aspx?scid=kb;en-us;823866

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Author Comment

by:eenlow
ID: 16987165
it almost sounds like people are spamming me and my server is trying to send a kickback but i want to be sure, you know...

thanks
Eric
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LVL 9

Expert Comment

by:Exchgen
ID: 16987178
USE SECOND LINK I GAVE YOU!!!

Connection filtering is a real nice feature and you would be away from most of the blacklisted IP's that are known to all small and big BLOCKLISTING companies.

Raghu
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