Updated 22/6/2016 – .NET 4.6.1 is supported for Exchange Server 2016 CU2 and Exchange 2013 CU13 or later. For safe installation of .NET Framework 4.6.1 use the following steps:

  1. Update servers to at least Exchange 2016 CU2 or Exchange 2013 CU13
  2. For each server in turn, place server into maintenance mode:
  3. Install the new .NET Framework on the server
  4. Install the applicable hotfix:
  5. After successful verification and testing, take server out of maintenance mode.

As always, check the Exchange Supportability Matrix when determining which versions of .NET Framework to install or update on your servers.

Previous article text below:

The Microsoft Exchange team has issued a warning to customers to not install .NET Framework 4.6.1 on Exchange servers.

We wanted to post a quick note to call out that since yesterday, the .NET Framework 4.6.1 has been made a recommended update on WU (Windows Update).

As we have already stated in the Exchange Supportability Matrix, at this time, this version of .NET framework is not supported by Exchange. In fact, we know of some issues if it is installed.

We are working with the .NET team to ensure that Exchange customers have a smooth transition to .NET Framework 4.6.1, but in the meantime, delay this particular .NET update on your Exchange servers (information on how this can be accomplished can be found in the KB article 3133990, How to temporarily block the installation of the .NET Framework 4.6.1).

Be cautious when approving updates in your WSUS or other deployment system, that you do not inadvertently approve the update for your Exchange servers.

Update: If you need to remove the 4.6.1 update from your servers follow Jeff Guillet’s advice here.

About the Author

Paul Cunningham

Paul is a former Microsoft MVP for Office Apps and Services. He works as a consultant, writer, and trainer specializing in Office 365 and Exchange Server. Paul no longer writes for Practical365.com.


  1. Janine J

    I am running Exchange 2016 CU1 on a Windows 2016 virtual server. Net 4.5.2 is installed on the server. I was planning to update Exchange directly to CU6 and have just performed the schema and AD updates by running the commands on a DC.

    I have now realised that I cannot install .net 4.6.2 onto the Exchange server as it is not supported with CU1. My thought is to upgrade to CU4 as it is compatible with .net 4.5.2, then install .net 4.6.2, then install CU6 (or maybe CU7).

    Is there an issue with installing CU4 after I have installed the schema and AD updates for CU6? Is there a better approach?

    I guess the moral of the story is apply updates regularly!

    1. Avatar photo
      Paul Cunningham

      Shouldn’t be a problem installing CU4 after applying the CU6 schema updates. And yes, you’re right to follow an upgrade path that keeps you within supported scenarios of .NET and CU levels.

      Yes, regular updates is good 🙂

  2. Dan

    I have a Exchange 2013 CU9 server with 4.6 and 4.6.1 installed. Single server, small environment with no apparent problems. Should I remove 4.6x or can i safely upgrade to CU13 and leave 4.6x loaded. Server OS is 2012r2.

    1. Avatar photo
      Paul Cunningham

      You should remove it, and only install it when you are running a supported build of Exchange.

      1. Dan

        Ok thank you for your response.

  3. Matt D

    Well dam, I updated all our exchange servers last night and now its business hours. Hopefully nothing happens today before tonight. I guess the question now is how will uninstall work, does it put the previous 4.5.2 back or does that need to be reinstalled?

  4. Bogdan

    Thank you Paul

  5. Pierre Lemieux

    Thank you Paul, you are always very helpful.

  6. jabarca

    Hi Paul,

    Thanks for the update! Do you happen to know if this issue will be affecting Exchange 2010. I was not able to find information about that. Just in case…

  7. opsmexc

    The original update was KB3102467 for .NET 4.6.1 (W2K12R2) and 3 others additionally this patch Tuesday: KB3122660, KB3127231, KB3098785 (if you already updated your server).

  8. Frank

    A KB number for the install in question would be helpful.

  9. Emmanuel

    Will this affect Exchange 2010? From what I read on the TechNet article “Mailboxes are quarantined and databases fail over unexpectedly in Exchange Server 2013”. If there are still more unknowns other than this then I will gladly hold off until there is a fix.

      1. Emmanuel

        Thank you sir! To be honest I didn’t know that Microsoft has an Exchange Supportability Matrix up until yesterday. I appreciate the info and quickly book marked it. 🙂

    1. TheUCGuy

      Hi Emmanuel,

      Pre 2013 versions of Exchange like 2010 only uses .Net framework 3.5.2 and hence it is a big jump to 4.6.1.

      And moreover no version of Exchange including 2016 supports .Net 4.6.1 and hence the answer is NOT to install it on your servers.

      1. Emmanuel

        Thanks, I appreciate the quick response.

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