Mac Mail (10.15.7) Heading is displayed but not content?

Hello thomasfromport ludlow,

Thanks for that info and for choosing the Apple Support Communities. If we understand correctly, you are having an issue with the Mail app on Mac. First, try running First Aid on your hard drive with the built in Disk Utility tool, as this can correct simple issues like you're experiencing.

How to repair a Mac disk with Disk Utility

Next, use safe mode to start up your Mac as it does the following things:

• Verifies your startup disk and attempts to repair directory issues, if needed
• Loads only required kernel extensions
• Prevents Startup Items and Login Items from opening automatically
• Disables user-installed fonts
• Deletes font caches, kernel cache, and other system cache files

Log in to your user account and test the issue while in safe mode and then restart normally and test the issue again.

How to use safe mode on your Mac

Graphics performance limited in macOS Recovery, safe mode, or Guest User mode

Cheers!