When you create a new contact, your emails with this person will have the Auto-share setting turned on. With this setting turned on, any emails between you and a saved contact will appear on their timeline. If you do not wish to share your emails with specific contacts, be sure to turn off Auto-sharing.
Your communication will remain private, unless you choose to change this from the black bar that will remain at the top of the contact’s timeline.
There are a few other rules to consider about private emails:
If you create a new contact from an email in triage, the contact will automatically become public unless you tick the option off.
If you assign an email from a private contact to yourself, the email will appear in your to-do list, but colleagues who are not members of the client team will not be able to see it.
If a public contact is copied in on an email from a private contact, that email will be visible on the public contact’s timeline.
If you create a contact using the global "+" button or from the Contacts area, your email communications will automatically be shared on related timelines unless you tick the option off.
If you would like to remove a specific email from a timeline (for example, you are having a non-work related conversation with a client), you can remove it by clicking the "X" under the 'Timeline' section of the information tray'