Hello,
It seems like you are facing an issue with the font size in Outlook 365 for displayed emails and emails being typed. Let's try to resolve this issue step by step:
Change Font Size for Displayed Emails: Open Outlook and go to the View tab. Click on View Settings. In the Advanced View Settings dialog box, click on Other Settings. Click on Column Font. Choose the desired font and size. Click OK. Click OK again to close the Advanced View Settings dialog box. Change Font Size for Composing and Replying Emails: Open Outlook and go to File. Click on Options. In the Outlook Options dialog box, click on Mail. Scroll down to the Stationery and Fonts section and click on Stationery and Fonts. Under the Personal Stationery tab, click on Font under New mail messages. Choose the desired font and size. Click OK. Under the Personal Stationery tab, click on Font under Replying or Forwarding Messages. Choose the desired font and size. Click OK. Click OK again to close the Signatures and Stationery dialog box. Click OK to close the Outlook Options dialog box. Additional Steps: Restart Outlook: Close and reopen Outlook to see if the changes take effect. Adjust Display Settings: Right-click on your desktop and select Display Settings. Under Scale and layout, make sure the setting is set to 100%. Click Apply and then OK. Alternative Method: If the above steps do not work, try resetting the Outlook view:
Close Outlook. Press Windows + R, type outlook.exe /cleanviews, and press Enter. Restart Outlook and check if the issue is resolved. If you continue to experience problems, it may be a good idea to repair your Office installation:
Close all Office applications. Open Control Panel > Programs and Features. Select Microsoft Office, click on Change, and choose Quick Repair or Online Repair. I hope these steps help you resolve the issue with the font size in Microsoft Outlook. If you continue to experience problems or need further assistance, please let me know.
Best Regards, Saurabh