Mac Outlook not responding with two external monitors connected

Dear Bill
Welcome and thank you for providing detailed information about the issue you are experiencing in Q&A forum. Based on your description, I understand that you are running into a difficulty using Microsoft Outlook (Version 16.101) on your MacBook Pro 16-inch (Nov 2023) with macOS 15.6.1 (24G90), where: 

• Outlook works fine with one external display connected. 
• Outlook becomes unresponsive/freezes specifically when you click on an email after connecting two external monitors. 

The freezing issue you’re experiencing when clicking on mail in Outlook is most likely caused by a software conflict related to how the application handles graphics and window rendering across multiple high-resolution displays. Outlook Version 16.101 is a relatively recent build that may include compatibility challenges affecting the rendering of new mail windows or previews in complex multi-display setups. This issue often becomes noticeable after recent macOS 15.6.1 updates, which can change how third-party applications like Outlook manage window behavior. Additionally, the problem is highly sensitive to your display configuration: inconsistencies such as differing resolutions, varying refresh rates, or mixing mirroring with extended mode between your two external monitors can easily trigger critical rendering faults, causing Outlook to freeze when opening new elements.

To address this issue, please attempt the following steps, checking if Outlook functions correctly after each one: 

1. Software Updates   

• Update Outlook: Ensure you are running the very latest version. Go to Help > Check for Updates within Outlook. Microsoft frequently releases patches for multi-monitor display issues. If the latest version is the problem, you may consider downgrading temporarily (see reference link below). 
• Update macOS: Check System Settings > General > Software Update to make sure you haven't missed a minor update, as these often contain critical graphics and system stability fixes. 
• Downgrade Outlook: If the issue started immediately after updating to version 16.101, you may need to revert to a previous, stable release while Microsoft works on addressing the compatibility problem. You can find older installer packages here: Update history for Office for Mac - Microsoft Learn 

2. Optimize Display Configuration 

• Standardize Resolution: Temporarily set all external monitors to the same standard resolution (e.g., 1080p or 1440p) to check if the difference in resolution is the root cause. 
• Synchronize Display Settings: Go to System Settings > Displays. Ensure all monitors have:  The same Scaling ratio, the same Refresh Rate, the correct display mode (Extended, not Mirrored). 

I hope this information is helpful in resolving your issue. Please try these steps and let me know if you encounter any other issues or if one of these solutions works for you. Feel free to share any further details, and I will be ready to assist! 

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