For your convenience, every address you send an email to or from which you receive an email gets added to your Recipients List. Think of the recipients list as "Contacts-lite" – addresses stored in the Recipients List don’t have the same level of detail as a full contact. If you do not wish to automatically add contacts to your recipients list, please make sure to disable this feature on the Settings page, by making sure the Auto-fill email addresses boxes are not selected.
To manage your Recipients list, go to Settings > Compose and click edit recipients list.
This will call up a window that contains all the addresses you’ve sent to and received from. You may choose to add any email address you like to your Contacts or delete it from the Recipients list altogether. Just click Ready when you’re finished. You may also delete all addresses from your Recipients List at once by clicking Delete all entries.