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We still have not uncovered the culprit on this part - but in the end, the blacklisting was caused by a laptop on the network (the CFO's laptop) that was filled with every bit of malware available. &nbsp; 
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We still have not uncovered the culprit on this part - but in the end, the blacklisting was caused by a laptop on the network (the CFO's laptop) that was filled with every bit of malware available.  

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Hi -<br />
<br />
When troubleshooting an on-and-off blacklisting issue for one of our clients, I habitually looked at the 'Allowed IPs' in the ESM. &nbsp;What blew my mind was when I found an external IP listed - 75.126.45.162. &nbsp;<br />
<br />
Once I removed the IP address, as you may guess the IP address was delisted the same day.<br />
<br />
To me, there isn't any logical reason it would be there other than someone purposely placing it there. &nbsp; But why? &nbsp; Puzzling. &nbsp; <br />
<br />
It's running on Windows 2000 Sp4<br />
Exchange Server 2000 Sp3<br />
Trend Micro A/V<br />
<br />
Ideas?
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Hi -

When troubleshooting an on-and-off blacklisting issue for one of our clients, I habitually looked at the 'Allowed IPs' in the ESM.  What blew my mind was when I found an external IP listed - 75.126.45.162.  

Once I removed the IP address, as you may guess the IP address was delisted the same day.

To me, there isn't any logical reason it would be there other than someone purposely placing it there.   But why?   Puzzling.   

It's running on Windows 2000 Sp4
Exchange Server 2000 Sp3
Trend Micro A/V

Ideas?

Exchange 2000 Server compromised?

Interactions between email servers and clients are governed by email protocols. The three most common email protocols are POP, IMAP and MAPI. Most email software operates under one of these (and many products support more than one).  The correct protocol must be selected, and correctly configured, if you want your email account to work.

Email Protocols

Within Internet message handling services (MHS), a message transfer agent or mail transfer agent (MTA) or mail relay is software that transfers electronic mail messages from one computer to another using a client–server application architecture. A MTA implements both the client (sending) and server (receiving) portions of the Simple Mail Transfer Protocol (SMTP). The terms mail server, mail exchanger, and MX host may also refer to a computer performing the MTA function. The Domain Name System (DNS) associates a mail server to a domain with mail exchanger (MX) resource records containing the domain name of a host providing MTA services.

Email Servers

Exchange is the server side of a collaborative application product that is part of the Microsoft Server infrastructure. Exchange's major features include email, calendaring, contacts and tasks, support for mobile and web-based access to information, and support for data storage.