Exchange 2013 CU1 Released

After a small delay the Exchange team have announced the eagerly awaited release of Exchange 2013 Cumulative Update 1!   Knowledge base article 2816900 contains a description of CU1.  This update will allow on premise installations to co-exist with Exchange 2007 and Exchange 2010.



Exchange 2013 CU1 Download

CU1 marks a change in how updates are going to be released and supported by the Exchange team, and this is detailed in a previous post.


As always check the Exchange 2013 system requirements to ensure that all support aspects have been met.  Exchange 2013 CU1 will support coexistence with Exchange 2007 SP3 RU10 and Exchange 2010 SP3 servers in the same Exchange organisation.  Just as before you cannot re-introduce a down level Exchange role once the last one has been removed.  For example if you want to maintain the capability to install additional Exchange 2007 servers ensure that you preserve at least one machine that has all the roles.  This will allow you to add more Exchange 2007 servers in at a later date.  The same also applies for Exchange 2010, once that role has been removed you cannot add additional servers back into the Exchange org.


Exchange 2013 RTM’ed at build  15.00.0516.032  and CU1 takes this build number to 15.0.620.29 


CU Is the New SP (well almost)

You can to start thinking of a CU like a service pack in previous versions of Exchange, though it is not 100% the same.  There are several good reasons for this:

  • A CU can update a previous install
  • A CU is a complete build of Exchange and CU1 can be used to install  a server – no need to install RTM bits and then have to upgrade them
  • You cannot uninstall a CU.  Removing the CU will uninstall Exchange 2013 from that server
  • CU may have Active Directory schema changes
  • CU may make additional Active Directory changes


Some Items For Consideration

  • Exchange 2013 sizing guidance is not yet finalised
  • CU1 requires AD and Schema changes, plan accordingly
  • Read the release notes to understand the impact on OAB downloads.  Unexpected full OAB downloads in a large environment are not a good thing….
  • Cannot uninstall a single role from a server, uninstalling a single role will remove both CAS and Mailbox.  This is a change from previous versions.
  • Mailbox sizes will be tracked more accurately and thus appear to be larger.  Make sure you understand what growth ratio is applicable in your environment based off moving pilot users. 
  • Exchange 2013 Public Folders can be accessed through Exchange 2013 OWA
  • Do not install this update (or any other for that matter) until you thoroughly test it in a lab
  • Do not install this update until you ensure that all 3rd party vendors have certified their product against it.  Hearing the words “Not Supported, sorry but you are on your own” is guaranteed to ruin your day…….


And for many customers who had issues with managers of Distribution Groups after moving to Exchange 2010 it is great to see that Group on Group action is back!!!  Groups in Exchange 2013 can now manage groups!




Note that Exchange 2013 does NOT support

  • Outlook 2003
  • Exchange 2003 co-existence in the same forest
  • Exchange 2007 SP3 RU9 or lower versions of Exchange
  • Exchange 2010 SP2.  Exchange 2010 SP3 is required for coexistence with Exchange 2010
  • Outdated Outlook 2007 clients (Outlook 2007 SP3 with November 2012 Cumulative Update is required)
  • Outdated Outlook 2010 clients (Outlook 2010 SP1 with November 2012 Cumulative Update is required)


Additional Resources

What's Discontinued in Exchange 2013

Exchange 2013 CU1 Release Notes

Exchange 2013 Release Announcement – especially the comments!

Exchange 2013 High Availability Changes in CU1


Keep a weather eye on the Exchange 2013 forums to see what feedback the community has!





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Comments (22)
  1. anonymouscommenter says:

    "Cannot uninstall a single role from a server, uninstalling a single role will remove both CAS and Mailbox.  This is a change from previous versions."

    I have to admitt I don't like this new behaviour as it is limiting the flexibilty of the Exchange deployments if roles needs to moved/removed.

    What is the reason behind this new behaviour?



  2. And there are a few forums comments on this too.  For example:…/1fd022ed-83a1-4832-9787-3c7eb0233f58



  3. anonymouscommenter says:

    Hi guys are there any changes to cross forest migration in this update? Technet suggests that cross forest migration is only available from Exchange 2013 to Exchange 2013 (…/ee633491(v=exchg.150).aspx).

    Can you preform a cross forest migration from Exchange 2010  to Exchange 2013  with SP3 for Exchange 2010 and CU1 for Exchange 2013?



  4. Hi Grant,

    That is possible, though the TechNet page above only talks about a specific migration scenario, which is the 2013 -> 2013 cross forest move.  

    I'll file an internal content update note to provide feedback on this.



  5. anonymouscommenter says:

    Thanks Rhoderick,  just to clarify is it possible without the service pack for 2010 and CU for 2013?



  6. anonymouscommenter says:

    Hi Rhoderick

    The following forums also indicated that it wasn't possible:…/6b3ff7b1-e9fe-42b7-8f4f-85b882fabde9…/c90a61cf-5f42-433f-ba1f-43d80d9b0d75



  7. Hi Grant,

    Back from a cheeky holiday  🙂

    Those links are the RTM build of Exchange 2013, not CU1.



  8. anonymouscommenter says:


    news on cross forest migration from legacy servers (2007 SP3 RU10) to 2013 CU1? I'm trying to do, but seems not to work…


  9. Hi Matt,

    What error etc are you seeing?  If I get a bit time tomorrow I'll try this out.

    Where URL are you using for the E2013 MRS proxy ?



  10. anonymouscommenter says:

    Hi i have two question, first it is posible to migrate (cross-forest) public folder from exchange 2010 to Exchange 2013 (this is supported?)? second it is posible to not delete user mailbox from sorce (Exchange 2010) after migrate (cross-forest ) to Exchange 2013?



  11. Hi Blazey,

    I don’t believe that the X-Forest scenario is currently written up on TechNet – This is the existing PF migration content…/ee861103(v=exchg.150).aspx

    I’ll follow up internally to see what the scoop is.



  12. anonymouscommenter says:

    Hi Rhoderick,

    Is the process for performing an Exchange 2010 to 2013 cross forest migration similar to an Exchange 2010 to 2010 cross forest migration?  Are there any advantages to having an Exchange 2013 CAS server in the 2010 source domain?



  13. Hi Luc,

    Yes  it is a similar process (compared to 2010).  Some details here…/ee633491(v=exchg.150).aspx

    As Blazey was asking, the one take back right now is around the PF migration.  I did not get anything more to share on that – sorry!

    Additionally InterOrg is not supported either, worth mentioning as that is PF related.



  14. anonymouscommenter says:

    Rhoderick, Any update on cross forest PF migration support? I see detailed instructions on technet for PF migrations to Exchange Online…but on prem is left out in the cold? What gives? -JB

  15. anonymouscommenter says:

    HI JB,

    Not yet, I have not seen anything more on the X-Forest PF migration.

    And could I ask you a question please. When you submitted the comment, were you signed into the site? Curious as it says “Anonymous” and I have seen that with all the recent comments. The blog platform was upgraded over the weekend and I want to make sure this is working as expected.


  16. anonymouscommenter says:

    When Exchange 2013 was released it heralded a different servicing strategy compared to Exchange 2007

  17. anonymouscommenter says:

    When Exchange 2013 was released it heralded a different servicing strategy compared to Exchange 2007

  18. anonymouscommenter says:

    We are now at the end of the Exchange 2013 RTM support lifecycle phase. Yes, it really has been two years

  19. anonymouscommenter says:

    Still no feedback regarding the PF cross forest migration from 2010 to 2013?

  20. Not heard/seen anything more on this Akr.


  21. anonymouscommenter says:

    Bottom line is – Microsoft don’t care about public folders for on prem customers – especially cross forest. You’ll have to use 3rd party tools. Try I’ve done a 2007-2013 cross PF migration. It works reasonably well although you’re on your own as far as sorting out mail enabled folders etc.

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