Forefront Online Protection for Exchange Spam Filtering to Outlook’s Junk E-Mail Folder

Forefront Online Protection for Exchange (FOPE) is a cloud hosted email anti-spam and antivirus filtering system. Amongst the options to filter away your spam, one of the options to to allow the email to be flagged and sent on into your on-premises email system, and then managing it there.

If you have Exchange 2007 or later it is possible to write Exchange Transport Rules to process this flagged email and move it directly to the Junk E-Mail folder in your mailbox. This allows users to have their probable spam in a different location from their inbox email, but not in a different system accessed external to their email client, for which they might need a second login account or a delay before receiving the notification email. This works for probable spam as much obvious spam is filtered out at the edge of FOPE and so cannot make it to a place where users can see it.

An additional benefit of this filtering inside Outlook or OWA to the Junk E-Mail folder is that users can mark messages as safe or blocked in the client and this is picked up by Exchange and can be sent automatically to FOPE, which means FOPE flags it as spam before it reaches the Exchange organization.

To configure this you need to set FOPE to flag spam with a X-Header. This is documented at various places online, but misses out one vital piece of information which I wrote this blog to document. The missing info is what the value of the X-Header is so that you can actually write a transport rule to process it.

In FOPE, select your email domain (under Domains) and on the domain page click Edit next to Spam Action under Service Settings. Change the Spam Action to Add X-Header and type the header name that you want to use:

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On your Exchange organization create a transport rule (these pictures are from Exchange 2007, but 2010 or 2013 are technically the same though visibly different). The transport rule is set to apply to messages when a message header contains specific words and the name of the header is the value set in FOPE previously (X-MoveTo-JunkEmail in this example). The value of the header will always read “This message appears to be spam.”.

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It is possible to use the when the message header contains text patterns and use the RegEx expression \w* to find emails with your header in it and containing a value (\w* means any letter or digit repeated), but as we know the value for the header is always “This message appears to be spam.” then using regular expression filtering is adding un-needed CPU cycles to the Exchange Server – only use RegEx when the value can vary.

Office 365 use this process to place your probable spam in Junk E-Mail. In their case the header is X-FOSE-spam.

The transport rule continues to set the spam confidence level to a high value of your choosing, and higher than the value we will set in OrganizationConfig below.

So this rule will take all emails the FOPE marks as spam and changes the spam confidence level (SCL) value to 9 (in this example). Finally we need to set the SCLJunkThreshold property of OrganizationConfig to a value below the value in the transport rule. Exchange will place all email that exceeds this threshold into the Junk E-Mail folder in Outlook:

Set-OrganizationConfig -SCLJunkThreshold 4

If you are running the Content Filter hygiene agent then you will also want to check the Get-ContentFilterConfig values for SCLRejectEnabled, SCLDeleteEnabled and SCLQuarantineEnabled are all set to false. This ensures that SCL values that are are high are not rejected or deleted, or sent to quarantine. As all your email should be filtered by FOPE if you are using it, and the firewalls at your company or receive connectors on Exchange should be blocking email not sent from the FOPE datacenters (in FOPE admin pages click Information tab and then the Configuration link to get the list of IP addresses). The content filtering agent can be used as a second filter on-premises but if you don’t want to throw away or reject spam at this second level (recommended in this scenario) then ensure that the filter rejection, delete and quarantine settings are disabled. If you want to delete probable spam then set the transport rule to 5 and the SCLDeleteEnabled to $true and the SCLDeleteThreshold value to 9. Don’t reject or use the on-premises quarantine features when using FOPE (the transport rule cannot process the quarantined messages for a start).

Finally for administrators, consider a Message Retention Management or Retention Policy to delete without recovery email in Junk E-Mail folder after 21 days. Also consider the FOPE Directory Sync tool to push the user lists to FOPE as this upload also includes the pushing of the safe senders information as well.

Now for your users, all probable spam is managed in their email client, integrated with safe sender lists and without resorting to another application to view and deliver false positives and spam they want to read!

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