This tutorial explains the steps for deleting contacts from the autocomplete and to turn off the auto addition of contacts in your Gmail Account.
Delete contacts from autocomplete
Sometimes it is very annoying to see unwanted contacts appearing in Compose Gmail window, when you start typing the email addresses in To, Cc or Bcc list. If you want to remove any contacts from this list then you need to do the following
1. Click on the contacts link on the left hand side of your Gmail
2. Select the contacts that you want to delete then Delete Contact option available under More Actions.
3. Now to reflect this change you need to logoff from your Gmail account and login again.
Disable auto addition of contacts
The main problem that I see with my growing unwanted Gmail contact is because of the Create contacts for auto-complete feature. This feature when enabled, automatically adds a new email address to the contact list while sending a message.
To turn off the auto addition of contacts, click the Mail settings available under the Gmail options.
In the General Settings, scroll down to Create contacts for auto-complete section and select the value as I’ll add contacts myself.
After doing this, click on the Save changes button available at the bottom of the General Settings screen.