Gray line showing up in inbound Outlook emails, how can I get rid of it?

Hi @Erin Hall, 

Thank you for posting your question in the Microsoft Q&A forum.  

From your information, this gray horizontal line showing up halfway through emails is highly a known rendering issue in New Outlook. Outlook uses Microsoft Word as its rendering engine, which can misinterpret HTML and CSS in emails.  

Up to now, Microsoft hasn't had any official article or notification about this situation. However, there're workarounds you can try in your New Outlook to see if it helps resolve this behavior:  

1- Resize the email window: In some cases, some customers reported that adjust the zoom or resize the reading pane can make the line disappear.  

2- Clear New Outlook app cache 

• Close the new Outlook app.  
• Pressing the Windows + R > Type or paste the following command olk.exe --devtoolsin the Run box and click OK (Be sure to include a space before the two dashes if typing the command manually)  
• In the DevTools window, click the Application button on the toolbar. 
• In the left pane, under the Storage section, find the https://outlook.office.com link under Local Storage. Right-click on this link and select Clear. 

• Still in the left pane, locate the https://outlook.office.com link under Cookies, right-click on it and select Clear. 

• Close the DevTools window. 

3- Update Outlook: Ensure you're using the latest version of Outlook.  

We sincerely apologize for any convenience that this issue may have caused you. For this issue, I encourage you to submit this feedback directly through the Microsoft Feedback Hub. Each submission is reviewed by our product team and helps inform priorities for upcoming updates.   

I know this isn't the answer you were hoping for, and I want you to know that I wish I had a way to change it for you directly.   

As community moderators, please understand for us that we do not influence product design decisions and have limited access to internal development details. Our role is to guide users to the right resources and support channels.   

We’re committed to improving the Outlook experience, and your input plays a key role in shaping future enhancements. Sharing your experience through this channel is the most impactful way to advocate for a change that would benefit you and other users.    

If you have any other questions or need further assistance, please don’t hesitate to reach out. We're happy to help. 

Wishing you a great day ahead.

Just set zoom to 100% it will stuck on bottom, it start to move when zoom is less 100%