Mail cannot save information about your mailboxes because there isn't enough space in your home folder

Mail will not open since Catalina upgrade. Receive this message and I have tried all the older solutions with previous Mail OS update issues. This message pops up when attempting to import mail messages. "Mail cannot save information about your mailboxes because there isn't enough space in your home folder". Same message when I attempted the index fix from past. What is the current fix for this?