Office 365 diagnostic tools

This tool will collect data from a client computer and identify issues: (easy for any non-technical user to install)

Client Performance Analyser: https://support.office.com/en-gb/article/Office-365-Client-Performance-Analyzer-e16b0928-bd38-423b-bd4e-b8402bc106aa?ui=en-US&rs=en-GB&ad=GB

This tool will collect and fix many Office 365 issues: (easy for any non-technical user to install)

Support and Recovery Assistant: https://diagnostics.outlook.com/#/?env=ExRCA

Connectivity Tester (versatile tool for Admins to check email headers, connectivity, and more...)

https://testconnectivity.microsoft.com/

Steps Recorder

This built-in tool from Microsoft is useful for recording the screen steps that result in problem symptoms. Ask the user to press the Windows logo key together with the "R" key (Win+R) and type "PSR", then click OK. Useage is self-explanatory: press the "Start" button to begin recording and "Stop" to finish; upon clicking "Stop" the user is presented with a "Save" button to save the recording as a .ZIP file.

The zipped file contains a single .MHT file (viewable in most web browsers) which contains slides, screen shots and technical notes recorded by the app. You'll never need to ask a user "Can you talk me through what happened?" again - now you can see it step-by-step for yourself.

Office uninstall tool

Download a tool and discover manual steps to completely remove vestiges of earlier Office versions: https://support.office.com/en-us/article/uninstall-office-from-a-pc-9dd49b83-264a-477a-8fcc-2fdf5dbf61d8

(Also worth going to Control Panel > Mail > [remove Outlook data files and profiles]