I am trying to delete a friend's old email address so it doesn't automatically pop up when I enter his name while addressing an email. I have removed it manually from the address book, but it still shows up in Mail.
How do I stop this happening?
Under Mail's "Window" menu select "Previous Recipients" and you can delete any address you don't want.
When the suggestion appears, just use the navigation to reach it then press delete on it, that's it.
I just wanted to add a note here that it is apparently not possible to delete previous recipients on iOS.
This only works to effectively "hide" the previous recipient from the previous recipients list on your phone. Apple still keeps a file with all your previous recipients in iCloud. When you completely "Erase all Content and Settings" and set up as a new phone, then sign in to iCloud all the previous recipients are restored.
In other words you have to do this painful process of deleting every previous recipient you don't want in the list individually every time you get a new iPhone/iPad or otherwise want to start from scratch and do a complete erase on your current device, even if you set up as a new device. This is easily replicated and proved. In fact I intend to go to an Apple Shop soon to demonstrate and question the behaviour and whether it's possible for Apple to delete information about who I've emailed.
The inconvenience is one thing but I'm more concerned about the privacy implications that Apple keeps a "previous recipients" master file that you don't have access to and whose entries can't be deleted. A similar situation exists for Mail on OS X though it appears to be a different previous recipients master file. That is, every time I do a clean install of OS X or even set up a new account and log in to iCloud, the Mail app shows a bunch of previous email recipients that aren't present in any email message!
Fantastic information for the government along with all your other metadata.
To delete a person’s old email address, in Mail go to the ‘Window’ drop down menu (just before 'Help') and click ‘Previous Recipients’.
Then click on the old email address you want deleted and click the ‘Remove from List’ button.