IMF: How to exclude recipients from IMF filtering

Microsoft recently released a hotfix for Intelligent Message Filter that adds functionality to exclude certain recipients from IMF filtering using an exclusive list, or only apply IMF to certain users using an inclusive list. The latter should be great for limited testing in a production environment.

You do need to call Microsoft PSS to get the hotfix mentioned in KBA 912587. This updates MSGFILTER.DLL to version 6.5.7650.22.

With the hotfix applied, you need to fire up regedit and
- create a new key called ContentFilter in HKLM\Software\Microsoft\Exchange.
- create a new DWORD value called CheckRecipients
- if you want to use an exclusive list - which means messages IMF will bypass (not scan) the message if ALL recipients in the message are on the list, modify CheckRecipients DWORD value you just created and type 2 in Value data
- Create a new Multi-String value called RecipList - and add names of recipients you want to exclude from IMF filtering.

Again, the emphasis is on all recipients - if there's a single recipient of a message not on the exclusion list, it will get scanned by IMF.

To do the opposite - create an inclusive list - change the value of CheckRecipients to 1, and add names of recipients who would like to get their messages filtered by IMF to the RecipList value.

It is not required to restart the server after you apply this hotfix.

Note: Calling PSS for required hotfixes that resolve particular issues is free. Just have the KBA number handy!