Exchange CAS Issues Leading to Client and OWA Becoming Inaccessible

Kuhns, Chris 101 Reputation points

For a while now, I have been having a few things happening.

  1. OWA will become in accessible with a 503 error. An IISRESET in powershell fixes it.
  2. Outlook Clients on PC, Mac, and phones will become inaccessible
  3. Both will become inaccessible (which is new)
  4. Today, the CPU spiked at 100 and W3WP.exe was to blame

Now, most of the time the issue started in the middle of the night 1 and 2. 3 and 4 happened in the middle of the morning. I suspect something is up with IIS for the two CAS servers.

It isn't SSL, I have already eliminated that as an issue. I have been dealing with this for months and I am at a loss getting support here.


Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Andy David - MVP 145.1K Reputation points MVP

    Is anti-virus installed or any other 3rd party software other than exchange?
    Are backups running during those times?

  2. KyleXu-MSFT 26,241 Reputation points

    @Kuhns, Chris

    After running the "IISReset", the client may lose the connection for a while. So, I think we need to solve the OWA issue first.

    I would suggest you update your Exchange to the last version first: Exchange Server build numbers and release dates

    If this issue still exist, try to open Event View to check whether there exist related Error Event during this issue occur.

    You can also check from the “C:\Windows\System32\LogFiles\HTTPERR”, check whether there exist detailed information about this issue.

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