XCON: How to Block Port 25 Access to an Exchange Server 5.5 Computer (316205)

SUMMARY

You can use the Routing tab, located in the Microsoft Exchange Internet mail connector (IMC), to apply routing restrictions such as Post Office Protocol version 3 (POP3), Internet Message Access Protocol, Version 4rev1 (IMAP4), Simple Mail Transfer Protocol (SMTP) and specific computer Transmission Control Protocol and Internet Protocol (TCP/IP) traffic. However, in certain circumstances you may only want to block port 25 connectivity to an Exchange Server 5.5 computer and still enable the other protocols to connect. This article describes how to block port 25 connectivity by selecting the IMC that is included in the Microsoft Exchange Server Administrator program.

MORE INFORMATION

The IMC snap-in is included in the Microsoft Exchange Server 5.5 IMC. You can use the Connections tab, located in the IMC snap-in, to block port 25 connectivity. To do so:

Start the Exchange Server 5.5 Administrator program.
Locate the Configuration container, and then click Connections.
In the right pane, click Internet Mail Service, click Properties, and then click the Connections tab.
Click the Specify by host from the Accept Connections check box.
Click Add, enter the IP Address of the computer that you want to accept connections from, type 255.255.255.255 for the subnet mask, and then make sure the Accept connection from this host check box is selected.
Click Add, enter the IP Address 0.0.0.0, subnet mask 0.0.0.0, and then make sure the Reject connection from this host check box is selected.

NOTE: Make sure that you maintain the IP 0.0.0.0, subnet mask 0.0.0.0, Reject rule as the last rule. Any rules that you create after this rule is applied are not maintained.
Click OK, and then restart Internet Mail Service so that the changes take effect.