Blocking Exchange e-mail attachments in SBS 2003 (chapter 5, book excerpt)

Good Monday to you!

Each day, I am posting up a few pages from my Windows Small Buisness Server 2003 Best PRactices book until SBS 2008 ships. Today we look at the native e-mail attachment blocking in Microsoft Exchange Server 2003 in SBS 2003 and also discuss content filtering….this is actually one ofthe really cool features in SBS 2003 (the atachement blocking capability).

Anyways – enjoy the read and the ride….harrybbbb

Harry Brelsford, ceo at SMB Nation,


Blocking Attachments, E-mails, and Content

There are some interesting capabilities that you might not know about in Exchange in SBS 2003 relating to attachment and domain blocking. Content filtering is another matter I’ll close this section with.

BEST PRACTICE: CRN reported in “Rivals Face Challenge As Microsoft Extends Its Antispam Technology” (http://crn.channelsuper­ that Microsoft will offer stronger anti-spam technology in Exchange Server 2003 in the first half of 2004. No other details available at press time but monitor Microsoft’s Exchange and TechNet sites for updated information. CRN at should be monitored as well.

Attachment Blocking

You likely recall the Remove E-mail Attachments page (Figure 4-14) in the EICW from Chapter 4. The function it performs is relatively straightforward: remove e-mail attachments of a certain type. But a question that continually arose during the fall 2003 hands-on labs for SBS 2003 concerned where this setting was being made in the background. Students asked if they could see where the EICW was setting this.

So I researched this by consulting with the Microsoft SBS program manager who owns this functionality and found that:

                      An SMTP “sink” is trapping the attachments and handling them according to the rule you set on the Remove E-Mail Attachments page.

                      There is no user interface (UI) to “see” where these settings are made or where this activity is occurring (other than the outcome, such as the attachment being removed or saved to a folder).


And don’t forget that we have Outlook 2003 as a backstop to also block common attachments in e-mail. This is covered later in the Outlook 2003 section of this chapter.

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Junk E-mail Blocking

Another popular question is what native ability Exchange has to block offensive e-mail domains as a poor man’s form of spam blocking (that is, using it instead of purchasing a third-party spam blocking tool). This is most easily accomplished by select and configure the Connection Filtering and Sender Filter tabs on the Message Deliver Properties dialog box that you see in Figure 6-6 (right-click Message Delivery and select Properties under Global Settings in the Exchange System Manager under Advanced Management in the Server Management console).

Figure 6-6

Get to know the Message Delivery Properties sheet if you want to engage in basic e-mail blocking inside of Exchange.

This e-mail blocking can also be accomplished painfully by creating an Active Directory contact object that has the offending e-mail name (such as and then adding it via the Delivery Restrictions tab (click the Add button beneath Reject messages from) on the Small Business SMTP connector Properties screen.

BEST PRACTICE: Of course, I saved perhaps the best junk e-mail blocking discussion for last. Near the end of the fall 2003 SBS 2003 hands-on lab tour in the US, a few students, already having worked with SBS 2003 at that point, waxed poetically about the effectiveness of the Outlook 2003 spam blocking capability. The consensus was it just works. A Microsoft employee echoed the same sentiment as “your Microsoft Research division dollars at work.” Couldn’t have put it better myself!

Content Filtering

Now for the bad news. Content filtering-as many of us know it in third-party spam filters that eliminate offensive e-mails selling Viagra and Vicodin-is not natively available in Exchange (but should be around mid-2004 as per the Best Practice earlier). Don’t be confused because some might think that the Content Restrictions tab on the Small Business SMTP connector Properties screen (Figure 6-6 above) is really performing a filtering function. It is not. It is allowing

e-mail of different priorities, etc. Note that I’ll cover spam blocking in it various forms (attachment blocking, e-mail and domain blocking, and content filtering) more in Chapter 11. You’ll recall that I briefly mentioned spam in Chapter 5. Stand by!


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