Formatting Issues Between New Outlook and Classic Outlook

Hi @Wu Josephine, 

Welcome to the Microsoft Q&A forum.  

Thank you for providing clear examples, we truly understand the impact and appreciate the time you took to document the behavior. Based on your description, emails sent from New Outlook can display with different font, spacing, and bullet hierarchy in Classic Outlook, and emails created in Classic Outlook can show reversed list levels in New Outlook. 

This occurs because New Outlook and Classic Outlook use different rendering engines to display the same message content. Classic Outlook uses a Microsoft Word based renderer, while New Outlook uses a modern web based renderer, so certain HTML styles and list structures can be interpreted differently. Nested bullets, manual indentation using Tab or spaces, and content pasted from Word or other editors commonly change how levels are recognized. 

Below are some alternative steps designed to address your situation effectively: 

1/ Begin by configuring and standardizing your compose settings in New Outlook. 

• Go to Settings > Mail > Compose and reply. 
• Under Message format, select HTML, then Save. 
• Under Font and text style, set the same default font and size you use for new messages and replies. 

• For your information: Change the message format to HTML, Rich Text Format, or plain text in Outlook - Microsoft Support 

2/ Then, proceed by creating lists using only the Outlook list tools. 

• Use the Bullets or Numbering buttons for every list item. 
• Use Increase indent and Decrease indent to create sub levels. 
• Avoid using Tab, spaces, or manual alignment to create hierarchy. 

3/ Continue by adjusting and restoring formatting for content imported from other sources. 

• Paste using the Keep text only option. 
• Re apply bullets, numbering, and headings using the toolbar after pasting. 
• Review the list levels by clicking into each section and adjusting indent with the indent buttons. 

4/ Conclude by verifying all details and applying a reliable format for complex layouts prior to sending. 

• Send a short test email to yourself and open it in both New Outlook and Classic Outlook to confirm the layout. 
• For long, heavily structured content, send it as a Word or PDF attachment or share a OneDrive link to preserve the layout. 
• If the issue continues, share one sample message and confirm whether it was sent as HTML or Plain Text so we can provide guidance specific to that format. 

As community moderators, we appreciate your understanding that our access to internal development details is limited. Our primary role is to guide users toward the appropriate resources and support channels. While we may not have visibility into deeper backend analysis, we’ll continue doing our best to support you within the scope of our responsibilities.   

I hope this information is helpful. Please follow these steps and let me know if it works for you. If you have any updates regarding the issue, please feel free to share them with me.    

Thank you for your patience and your understanding. If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.    

I look forward to continuing the conversation. 

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