Custom (aka. Extension) attributes in Exchange 2010 SP2 and their use


Some of sharper readers of our documentation talking about schema changes that Exchange makes (see Exchange Server Active Directory Schema Changes Reference, November 2011) have noticed that in Exchange 2010 SP2, we have added several things that sound very related to what’s traditionally known as “custom attributes” in Exchange. Specifically:

For object class ms-Exch-Custom-Attributes we added:

  • ms-Exch-Extension-Attribute-16 to 45
  • ms-exch-extension-custom-attribute-1 to 5

There have been some questions regarding this; namely – are all of those for you to use? Does this mean that you now have all of those attributes to modify to your heart’s content? What’s the difference between all those things anyway?

Here’s the scoop:

For a while now, Exchange provides 15 custom attributes. Those are still there and you are free to use them as you used them before. They are known as CustomAttribute1 to 15 (or can also be referred to as ms-Exch-Extension-Attribute1 to 15). For more on those, please see this. So nothing has changed with those.

New! In Exchange 2010 SP2, we have added five new multi-value custom attributes that you can use to store information for mail recipient objects. They are the ExtensionCustomAttribute1 to 5 (also can be referred to as ms-exch-extension-custom-attribute-1 to 5). For the list of CMDlets that support those, please see this.

New! Finally, we have also added ms-Exch-Extension-Attribute-16 to 45. Those are not exposed to various CMDlets and Exchange management UI, because they were added for future use. As such, we cannot recommend that you use non-Exchange tools to edit their values because we might use those attributes in the future for various Exchange features. If and when we add management tools access to them, we will definitely let you know!

Nino Bilic

Comments (8)
  1. Charles Derber says:

    Is it possible to extend(add more value) the user’s attribute(e.g. manager field) as extended the schema…?

  2. Michael B. Smith says:

    I include some additional detailed information on the attribute changes here:

    theessentialexchange.com/…/a-somewhat-detailed-look-at-exchange-2010-service-pack-2-schema-changes.aspx

    ~Michael B.

  3. Andrew.Tucker says:

    Are these going to go into Live@Edu?

  4. HotFix says:

    I'm a little dissapointed that whoever thought to add the new Custom Attribute 1-5 didn't think there might be some confusion with the existing attributes "known as CustomAttribute1 to 15" and give them a slightly different name other than ms-exch-extension->custom<-attribute-1 to 5. I realize in the schema they are labeled differently but as you pointed out the pre-existing ones have been known as Custom Attributes since the pre-Exchange 2000 days.

    I can see now where any time Custom Attribe 1-5 is being discussed, we have forever and a day have to clarify which one set we are talking about.

  5. David says:

    Definitely not a good idea.  You shouldn't put something out there that contiguously follows customer-editable attributes and then possibly decide later that they are reserved for MS.  You really should call those

    ms-Exch-Reserved-Extension-Attribute-1 to 30 (or something similar) .  Then it will be clear for all of those companies that have already consumed 1 – 15 and are gambling that they can have those too.

  6. HotFix says:

    Just so the point isn't lost – are you all going to update the Exchange EMC to refer to the Custom Attribute 1-15 to Extension Attribute 1-15? Otherwise how are we going to differentiate between the old custom attribute 1-15 and the new custom attribute 1-5?

  7. wrong attribute names says:

    OK lets correct this article. The attribute names refered by this article are

    1) msExchExtensionAttribute16 to msExchExtensionAttribute45 not ms-Exch-Extension-Attribute16 to ms-Exch-Extension-Attribute45

    2) the old 15 Exchange custom attributes are extensionAttribute1 to extensionattribute15

    3) the extensionCustomAttribute1 to extensionCustomAttribute 15 don´t exist on Exchange 2010 SP2 there are 5 addition attributes msExchExtensionAttribute1 to msExchExtensionAttribute5

  8. paetzold@rz.rwth-aachen.de says:

    OK lets correct this article. The attribute names refered by this article are

    1) msExchExtensionAttribute16 to msExchExtensionAttribute45 not ms-Exch-Extension-Attribute16 to ms-Exch-Extension-Attribute45

    2) the old 15 Exchange custom attributes are extensionAttribute1 to extensionattribute15

    3) the extensionCustomAttribute1 to extensionCustomAttribute 15 don´t exist on Exchange 2010 SP2 there are 5 addition attributes msExchExtensionAttribute1 to msExchExtensionAttribute5

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