Here’s how to do this using any Mac running OS X 10.8 (Mountain Lion) or higher.
If so, take the following steps to finish setting up read receipt requests.
Highlight the entire line.
Copy that highlighted line with theCommand+Cshortcut, but don’t paste it yet.
End it with a single quote.
Disable Automatic Read Receipt Requests
Turning off this setting is just as easy.
As above, openTerminalagain.
throw in the following, then pressEnter:
defaults delete com.apple.mail UserHeaders
