How do I troubleshoot Office 365?

To troubleshoot Office 365 there are a number of tools which can be used. Depending on the scenario you are troubleshooting will depend on the tool you need to use.

What is the first troubleshooting tool to use?

A good starting point in troubleshooting Office 365 client applications is the Microsoft Support and Recovery Assistant (SARA) tool. Each time you tune the tool it checks for updates. The tool is downloading updates to its known scenario database. Once you get into the tool you will have options to run scenarios for Office, Outlook, Dynamics 365, OneDrive for Business, Skype for Business and advanced diagnostics.

How to check for known Outlook issues

Microsoft used to promote a support tool called OffCAT. The replacement to this tool is the Outlook scan option from the advanced diagnostics menu in the Microsoft Support and Recovery Assistant (SARA).

This is particularly useful if you are troubleshooting an Outlook issue. It can highlight known scenarios such as:

  • Over 500 folders cached into a single .OST file.
  • PST files attached to the Outlook profile on a network drive.
  • Disabled Hardware acceleration.
  • Third-party add-ins.
  • Plus many others.

Microsoft has an article on how to run this scenario, and save the results into JSON and HTML files for later review on another computer.

If you can get to a point where the Outlook scan contains no warnings or critical errors; You are then in a much better situation to continue troubleshooting beyond what can be detected in the Outlook client itself.

Other tools to troubleshoot Office 365

Remote Connectivity Analyzer

The Microsoft Remote Connectivity Analyzer has been around for a number of years.

It is a useful tool for checking connectivity to resources in both Office 365 and Microsoft productivity servers and services within your corporate network.

Client Application Logging

Presuming you have a support case open with Microsoft support; You may asked to enable logging to collect ETL or other logging files.

Further information on this for Outlook logging is available here.

Other Office 365 client applications may also have the capability to create ETL files.

Only Microsoft support have the ability to read ETL files.


If all the above tools do not provide the level of detail needed, or simply do not expose what an issue is, it becomes necessary to collect a Fiddler network trace of the issue.

With HTTPS decryption enabled, we can get visibility into the SSL tunnel to see the client and server request/responses.

Tracing with Fiddler is particularly useful for Office 365 clients and any web based application.

Office 365 Fiddler Extension

Taking the use of Fiddler one step further, reviewing the data collected with the Office 365 Fiddler Extension gives you a lot of accumulated knowledge to assist in troubleshooting.

See the post on the Office 365 Fiddler Extension for more information on how this tool can assist troubleshooting!