Using classic Outlook for Windows in business environments
Hi Karen,
Based on my research, there seems to be no supported option in Classic Outlook for Windows to independently change the font size of the message header fields such as To, Cc, Bcc, or Subject.
The font settings available under File > Options > Mail > Stationery and Fonts apply to the message body (new messages, replies, and forwards), not to the recipient or subject fields.
If this functionality is important for your workflow, I recommend submitting feedback through Feedback Hub. This is the most effective way to ensure your voice reaches the product team and can be considered for future improvements.
Once you've submitted your feedback, feel free to share the link here in the comments. I’ll be happy to upvote it to help bring more visibility.
I hope this information is helpful. Let me know if you have any questions.