Microsoft Online Services Diagnostics and Logging (MOSDAL) Support Toolkit.

The MOSDAL Support Toolkit performs network diagnostics and collects system configuration, network configuration, and logging information for service-based programs that are installed on the computer. The logs that the tool generates provides data to help troubleshoot configuration, network, installation, and other service-related issues.

The MOSDAL 4.0 release introduces the following enhancements:
•Improved user experience and user interface
•Training completely revamped to include troubleshooting scenarios and diagnostics
•Increased number of Microsoft Knowledge Base articles that show how to use MOSDAL
•Added configuration file for system flexibility and modularity
•Added user account control management and Active Directory Federation Services (AD FS) PowerShell commandlets
•Additional Directory Synchronization diagnostics information captured
•Changed localization management to a more manageable solution

This tool will help troubleshoot issues with Office 365.

This post also contains links to resources such as Microsoft Knowledge Base articles, troubleshooting videos, and TechNet Radio webcasts that show how the tools are used to diagnose and resolve specific Office 365 scenarios.

Also see Office 365 Mail Flow Troubleshooter from Microsoft.