Finally Microsoft released tool to check your internet connection for Office 365.
Long time ago we had microsoftspeedtest.com but this tool has not been available for many months now.
But now we have new tool:
Office 365 Network Analysis Tool.
This tool is web-based and can check:
- port connectivity
- route paths between the client and tenant
- bandwidth speed and capacity test
- VoIP readiness
This tool can be found at:
English 
polski