Outlook 2003 has stricter security controls over the presentation of rich content sent in e-mails. E-mail with HTML containing ActiveX controls, for
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instance, is one of the biggest vectors for spyware or virus infections. As an additional security measure, Outlook 2003 does not download images by default when users open HTML e-mails. This conserves bandwidth and protects users from questionable images (for instance, in the context of pornographic spam e-mail).
If you right-click on an image in an e-mail sent to you and select "Change Automatic Download Settings," you can modify the way Outlook handles image downloads depending on the e-mail's originating domain. The "Don't download pictures or other content automatically" option is usually enabled by default, but there are two other settings that deserve attention:
1. "Permit downloads…from Safe Senders/Recipients" uses Outlook's Junk E-mail filter's whitelists to determine if the mail in question is safe to load pictures for. This is only useful if the Junk E-Mail filter's whitelists are in use in the first place. However, if you're relying on a server-side filtering system that doesn't interact directly with Outlook, this won't be as valuable.
2. "Permit downloads … from Trusted Zone [sites]" is a little more helpful. The Trusted Zone in Internet Explorer can be managed through IE's own control panel, or through third-party tools like the Internet Explorer Power Tweaks Web Accessories pack, or by editing the registry directly. This option makes it possible to define, either through policies or perhaps a script, what sites are recognized as safe throughout your organization.
Unfortunately, Outlook does not perform reverse DNS checking to determine if a given e-mail did actually originate from the server it claims to be from. This makes it possible for someone to send spoof e-mails that claim to be from a specific domain -- and may even load pictures from that domain -- but aren't in fact from that location. It's largely your server's responsibility to filter out these mails, and the tools now exist to do so.
Serdar Yegulalp is editor of the Windows Power Users Newsletter and a regular contributor to SearchExchange.com.
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This was first published in May 2005