how can I change the column width in my apple mail

Hmm. That's beyond my level of knowledge. Sounds like I have to live with it, and report to Apple.

That is a tough one, there is something corrupted, possibly a .plist file...

/Users/YourUserName/Library/Mail/V6/big.long.hex.number/INBOX.mbox/Info.plist

Maybe...

/Users/YourUserName/Library/Preferences/com.apple.spaces.plist

Hi Milad,

If your talking about the Message list, grab the tiny dividing line in the header row & drag it. :)

The column width continues to return to a narrow setting each time I use Mac Mail. How can I get the width to remain at the size that I prefer when I drag the dividing line?

Apple my be able to help you with it, good luck my friend. :)