Slightly Off KIlter

Up until sometime today, my incoming email was in Rich Text (HTML) mode if that's the way the sender sent it. I send my mail out in plain text, but I was happy to read mail in whatever form the sender preferred.
In many cases, Rich Text really is better.

Today, something changed. I started seeing all of my incoming mail in Plain Text mode. Ugh.

Here's the difference between Rich Text and Plain Text for one type of email I get regularly — Job Postings from simplyhired.com:

Rich Text (Best Alternative)

---

Plain Text

I really do not want to try to read those in "Plain" text. (shudder)

It's possible to switch between the two alternatives on a message-by-message basis, using the 'View >> Message' menu. But all my messages were in PlainText; I didn't want to pull down a menu to fix each one individually. I wanted to get back to Rich Text by default.

I did some web searching and found several recommendations. Some people suggested I needed to run:

defaults write com.apple.mail PreferPlainText 0

That didn't work.

Then I found some more recent discussions that recommended running:

defaults write com.apple.mail PreferPlainText -bool FALSE

That didn't work either.

In frustration, I opened ~/Library/Preferences/com.apple.mail.plist directly in Xcode and searched for PreferPlainText. It seems to (now?) want either YES or NO as a value.

I set the value to NO and saved, then relaunched Mail.app.

HTML (Rich Text) mail is back.

I still don't know what I did to make it disappear!