Delete old email addresses
Mail keeps a list of your previous recipients and uses it to suggest or complete addresses for you when you send email. You can delete obsolete or incorrect addresses from the list in Mail, and use the list to quickly see or add people to the Contacts app.
In Mail, choose Window > Previous Recipients.
Do any of the following:
Sort the list: Click a column header.
Search for a name: Enter the name in the search field.
Remove a name from the list: Select one or more names, then click Remove From List.
Show a name in Contacts: Double-click any name that’s preceded by a card icon.
Add a name to Contacts: Select a name, then click Add to Contacts.
Tip: If you use Smart Addresses, you can remove a recipient from the list when you address a message by clicking the arrow in the address.
If you use iCloud Contacts, your Previous Recipients list is available on your other Mac computers (with OS X v10.8 or later) and iOS devices (with iOS 6 or later) that have iCloud Contacts turned on.