Microsoft Exchange Server 2010 : Configuring Anti-Spam and Message Filtering Options (part 1) - Filtering Spam and Other Unwanted E-Mail by Sender, Filtering Spam and Other Unwanted E-Mail by Recipien

Every minute users spend dealing with unsolicited commercial e-mail (spam) or other unwanted e-mail is a minute they cannot do their work and deal with other issues. To try to deter spammers and other senders from whom users don't want to receive messages, you can use message filtering to block these people from sending messages to your organization. Not only can you filter messages that claim to be from a particular sender or that are sent to a particular receiver, you can also establish connection filtering rules based on IP block lists. The sections that follow discuss these and other anti-spam options.

As you configure message filtering, keep in mind that while Exchange Server 2010 is designed to combat most spammer techniques, no system can block all of them. Like the techniques of those who create viruses, the techniques of those who send spam frequently change, and you won't be able to prevent all unwanted e-mail from going through. You should, however, be able to substantially reduce the flow of spam into your organization.

Filtering Spam and Other Unwanted E-Mail by Sender

Sometimes, when you are filtering spam or other unwanted e-mail, you'll know specific e-mail addresses or e-mail domains from which you don't want to accept messages. In this case, you can block messages from these senders or e-mail domains by configuring sender filtering. Another sender from which you probably don't want to accept messages is a blank sender. If the sender is blank, it means the From field of the e-mail message wasn't filled in and the message is probably from a spammer.

Sender filtering is enabled by default. To configure filtering according to the sender of the message, follow these steps:

1. Start the Exchange Management Console. On an Edge Transport server, select Edge Transport, click the server you want to work with, and then click the Anti-Spam tab in the details pane. On a Hub Transport server for which you've enabled spam filtering, expand the Organization Configuration node, select Hub Transport, and then click the Anti-Spam tab in the details pane.

2. Right-click Sender Filtering, and then select Properties. The Sender Filtering Properties dialog box appears.

3. On the Blocked Senders tab (shown in Figure 1), the Senders list box shows the current sender filters, if any.

   

   Figure 1. Use sender filtering to set restrictions on addresses and domains that can send mail to your organization.

4. You can add a sender filter by clicking Add. In the Add Blocked Senders dialog box, select Individual E-mail Address if the filter is for a specific e-mail address, or select Domain if you want to filter all e-mail sent from a particular domain. Type the e-mail address or domain name, as appropriate, and then click OK.

5. You can remove a filter by selecting it and then clicking Remove.

6. To edit a filter, double-click the filter entry, enter a new value, and then click OK.

7. On the Blocked Senders tab, you can also filter messages that don't have an e-mail address in the From field. To do this, select the Block Messages That Don't Have Sender Information check box.

8. On the Action tab, specify how messages from blocked senders are to be handled. If you want to ensure that Exchange doesn't waste processing power and other resources dealing with messages from filtered senders, select the Reject Message option. If you want to mark messages as being from a blocked sender and continue processing them, select Stamp Message With Blocked Sender And Continue Processing. Click OK.

Filtering Spam and Other Unwanted E-Mail by Recipient

In any organization, you'll have users whose e-mail addresses change, perhaps because they request it, leave the company, or change office locations. Although you might be able to forward e-mail to these users for a time, you probably won't want to forward e-mail indefinitely. At some point, you, or someone else in the organization, will decide it's time to delete the user's account, mailbox, or both. If the user is subscribed to mailing lists or other services that deliver automated e-mail, the automated messages continue to come in, unless you manually unsubscribe the user or reply to each e-mail that you don't want to receive the messages. That's a measure that wastes time, but Exchange administrators often find themselves doing this. It's much easier to add the old or invalid e-mail address to a recipient filter list and specify that Exchange shouldn't accept messages for users who aren't in the Exchange directory. Once you do this, Exchange won't attempt to deliver messages for filtered or invalid recipients, and you won't see related nondelivery reports (NDRs), either.

Recipient filtering is enabled by default. To configure filtering according to the message recipient, follow these steps:

1. Start the Exchange Management Console. On an Edge Transport server, select Edge Transport, click the server you want to work with and then click the Anti-Spam tab in the details pane. On a Hub Transport server for which you've enabled spam filtering, expand the Organization Configuration node, select Hub Transport, and then click the Anti-Spam tab in the details pane.

2. Right-click Recipient Filtering, and then select Properties. The Recipient Filtering Properties dialog box appears.

3. On the Blocked Recipients tab (shown in Figure 2), the Recipients list box shows the current recipient filters, if any.

   

   Figure 2. Use recipient filtering to set restrictions for specific or invalid recipients.

4. You can filter messages that are sent to recipients who don't have e-mail addresses and aren't listed as recipients in your Exchange organization. To do this, select the Block Messages Sent To Recipients That Do Not Exist In The Directory check box.

5. Before you can add other recipient filters, you must select the Block Messages Sent To The Following Recipients check box. You can then add a recipient filter by typing the address you'd like to filter and then clicking Add. Addresses can refer to a specific e-mail address, such as [email protected], or a group of e-mail addresses designated with the wildcard character (*), such as *@blueyonderairlines.com to filter all e-mail addresses from blueyonderairlines.com, or *@*.blueyonderairlines.com, to filter all e-mail addresses from child domains of blueyonderairlines.com.

6. You can remove a filter by selecting it and then clicking Remove.

7. To edit a filter, double-click the filter entry, enter a new value, and then press Enter. Click OK.