Configuring the SMTP Message Screener in Visual C#.NET

Encode QR in Visual C#.NET Configuring the SMTP Message Screener

Use This Setting To Provide a string that the Message Screener will look for in e-mails. You can select whether the action is applied if the keyword is found in the message header, the body, or both. You can also specify an action for when a message meets the keyword criteria. You can configure the Message Screener to delete the message, hold the message, or forward the message to a specified mailbox. Add the names of senders or of entire domains for which e-mail will be blocked. When the SMTP sender address matches the blocked senders or domains list, the message will be deleted.

Tab Keywords (see Figure 9-5)

Users/Domains (see Figure 9-6)

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Tab Attachments (see Figure 9-7)

Use This Setting To Configure how Message Screener will filter attachments. You can configure Message Screener to filter attachments based on attachment name, attachment extension, or attachment size limit. You can also specify an action for when a message meets the attachment criteria. You can configure the Message Screener to delete the message, hold the message, or forward the message to a specified mailbox.

Exam Tip Notice that you can configure the SMTP Message Screener to delete a message, hold a message, or forward a message to a specified mailbox if it meets the Message Screener criteria. Check this setting if Message Screener is blocking messages from getting to a user mailbox as expected, but other expected actions are not happening.

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Figure 9-6

Figure 9-7

For more information about configuring the SMTP application filter and Message Screener, see the Technet article, Using the ISA Server 2004 SMTP Filter and Message Screener, located at http://www.microsoft.com/technet/prodtechnol/isa/2004/ plan/smtpfilter.mspx.

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The SMTP filter must be installed on the ISA Server that is used to publish SMTP servers and used to configure access rules for sending SMTP messages to the Internet. However, because Message Screener need not be installed on a computer running ISA Server, you have several options for deploying Message Screener. One of the questions that you must address when deploying SMTP Message Screener is where to install the Message Screener component. You have two options:

Install Message Screener on ISA Server You can install Message Screener on the server running ISA Server and configure it to filter inbound messages. In this configuration, ISA Server Firewall services forwards all messages to the SMTP service which scans the messages. This configuration is less secure than installing Message Screener on another server because Message Screener requires that the SMTP service be installed on the ISA Server computer. Moreover, this configuration is not scalable for larger organizations. For these reasons, installing Message Screener on ISA Server is recommended only for situations in which no additional servers are available and in which ISA Server is not operating as an Internet-edge firewall. Install Message Screener on another IIS server This is the more secure configuration because the IIS Server running the SMTP service is not directly accessible from the Internet. The configuration is shown in Figure 9-8. The ISA Server can filter the SMTP commands, and only allowed packets will reach the SMTP Message Screener server. This option is also scalable because the Firewall service and SMTP Message Screener are separated. For maximum security, the IIS Server running Message Screener should be located in a perimeter network and the server should not be a member server in the internal domain. However, if the SMTP server is not a member of the internal domain and is also configured as the SMTP relay server for Post Office Protocol 3 (POP3) or Internet Message Access Protocol 4 (IMAP4) clients, users will not be able to authenticate to this server to relay messages. Installing the Message Screener component on a server in the perimeter network requires additional ISA Server configuration because you must configure server publishing rules or access rules between the perimeter network and the internal network, but this option is more secure.