Further to the above, I have now found the following in these Discussions, but under OS 10.5 (Leopard).
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MulderOct 3, 2008 1:50 PM Re: turning off previous recipient memorization
Re: turning off previous recipient memorizationin response to Chris R.If you want to disable the Previous Recipients feature, you can do it with this command in Terminal:
defaults write com.apple.mail SuppressAddressHistory -bool true
Neither Mail nor Address Book should be running at the time you do this. As the OP stated they don't want anyone in that list except people who are in their Address Book, if they add someone to their address book, they will need to reverse this command before that person could be added to the Previous Recipients list.
Mulder
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Before I risk trying this, can anyone tell me whether it will work or, on the contrary, do terrible things in Mountain Lion (10.8.5)? And if it works, will
defaults write com.apple.mail SuppressAddressHistory -bool false
restore the function, should I wish to do so at a later date?
Many thanks in anticipation.