Although you can currently use Office 365 Client Performance Analyzer (OCPA) to do connectivity diagnostics for both Exchange Online (EXO) and SharePoint Online (SPO), you will find in the latest tool version that recommended tool for making a troubleshooting and assessment analysis to check Office 365 access is now SaRA (Support and Recovery Assistant for Office 365):
If you install SaRA, you will see it’s a tool much more complete in regards of features available (as I will show you in future sots) that centralizes different support options for typical issues and problems with e-mail, OneDrive for Business, etc and it also allows to make advanced connectivity diagnostics: