Lately we have been fielding a lot of questions about why [SPAM] and [SURESPAM] messages keep on sliding through to the end users. We have also seen a lot of activity with users complaining about SPAM making it to them uninterrupted when it comes from an email address within their domain. Here is the problem:
In nearly all cases that we investigated, the user actually whitelisted their own domain or their own domains email address.
Why would this happen? Well, users tend to scan messages and look for familiar names and subjects. When they encounter something they recognize, like an email address from their colleague or from themselves, they trust the sender. When they trust the spoofed address, all future mail comes through, causing frustration for everyone involved.
Advise your users not to trust their own email address space when it shows up in ExchangeDefender SPAM reports. ExchangeDefender only intercepts messages going in and out of the organization, it does not filter internal messages. Any mail with the domains address space caught by ExchangeDefender is highly likely to be spoofed.
Of course, usage and configuration of ExchangeDefender is up to you, we make the product flexible enough to allow you to set your own policies. But blindly trusting entire domains and mirrored trust sets (from exchangedefender.com to exchangedefender.com for example) will only let dangerous items through. Consider tightening up the ship if you are seeing ExchangeDefender starting to slip, our metrics show that our detection rate keeps on going up as both volume and percentage.
As always, thanks for letting us clean your mail.