If recipients can’t read email you send them
If recipients can’t read your email messages because they contain strange characters, you can try changing the encoding to UTF-8, a universal encoding that’s compatible with a wide range of email clients.
Change your encoding preference to UTF-8
In iCloud Mail, choose Preferences from the Action pop-up menu in the sidebar.
Click Composing.
Select “Send outgoing messages using Unicode (UTF-8).”
Click Done.