One of the subtle changes in Mail in OS X 10.6 is the way the Copy Address contextual menu works. In previous versions of Mail, when you Control-clicked on an address and selected Copy Address, the user's e-mail address would be copied to your clipboard. In 10.6, though, Mail does some additional copying and formatting: you get the person's full name, and then the e-mail address enclosed in angle brackets.
If, like me, you copy and paste a lot of e-mail addresses from Mail, and want just the e-mail addresses, this change means a fair bit of annoying post-processing work. I either have to manually edit the address after pasting, or use my text editor's search and replace features to strip out the e-mail address from the pasted values. Not a lot of fun, to say the least.
Thankfully, Apple included a hidden preference to revert to the 10.5 behavior of copying only the e-mail address. Quit Mail if it's running, then enter this command in Terminal (in Applications -> Utilities):
defaults write com.apple.mail AddressesIncludeNameOnPasteboard -bool NO
Restart Mail, and Copy Address will once again do just what it says, which is the preferred behavior for my use of Mail. If you try this and decided you prefer the default version, quit Mail and run this command in Terminal:
defaults delete com.apple.mail AddressesIncludeNameOnPasteboard
This story, "Force Mail in 10.6 to Only Copy E-mail Addresses" was originally published by Macworld.