Unfortunately, what follows is for outgoing messages only. I was incorrect. I haven’t found a way to properly change the reading setting from Automatic to UTF-8
I don’t think this is a bug per se, but it is a bit unintuitive.
For practice I’ve started reading / writing emails in Chinese. The text encoding on Mac Mail by default is set to “Automatic”, and it never seems to guess UTF-8 right. At least not the emails I am getting. They come through garbled. However, when I choose Message > Text Encoding > Unicode (UTF-8) the emails will render fine.
It’s kind of a pain to do that for every message though. I looked though Preferences and there isn’t a setting anywhere to set the default encoding (which I find kind of odd) - or rather to change “Automatic” to something specific.
However, the fix is pretty easy. Just pop open a terminal and type:
$ defaults write com.apple.mail NSPreferredMailCharset "UTF-8"
quit and reopen Mac Mail and the Message > Text Encoding menu should now look like this:

I like that defaults program :)
That doesn’t seem to work for me. The text encoding menu always reverts to “automatic” even after I’ve done that incantation in Terminal. Any thoughts?
Yeah, I fooled myself with this. The setting sets your outgoing mails encoding. After I had done it I was verifying the emails were set to UTF-8 and happened to click on the ones that I had set to UTF-8 in the menu. It remembers the encodings per email.
I am still looking for a way to set the reading encoding, but I am having little luck.
It’s not working for me either… The text encoding menu always reverts to “automatic” even after making the change in Terminal.
It worked for my coworker (using the same exact version of Mail)… and nearly identical machines (his is a little bit newer MacBookPro)
HELP! it’s such a pain in the arse having to set that everytime!
[...] Setting Mac Mail to UTF-8 [...]