After posting the Exchange 2007 OPATH intro and How to Upgrade the Filters posts to EHLO over the past few days, one question that's come up enough to warrant another blog post is "Do I really need to upgrade my filters".
And the answer is pretty straight forward: maybe.
Ok, that's not fair. Let me explain...
If you want to update your existing legacy-version LDAP filter to have some new criteria, and you want to manage it from Exchange 2007 -- you'll need to upgrade the filter.
If you want to update your existing legacy-version LDAP filter to have the same criteria, but you want to start managing it from Exchange 2007 -- you'll need to upgrade the filter.
So what does that leave? Well, if you're perfectly content with the function of your current filter and you have no need to manage it from Exchange 2007 -- you don't need to upgrade the filter!
That's pretty key, as it probably describes a large number of the custom filters in use out there today. My advice: Save yourself the effort of doing the upgrade and just let it keep working as-is until you NEED to upgrade it...
Also, keep in mind that in most cases there's not a significant incentive to actually upgrade your existing filters. It's probably easier and less disruptive to create a new address list or email address policy from Exchange 2007 that has your desired filter (ideally a "precanned" filter created by GUI) and then decommission the old AL or EAP it replaces.