Hi @NWong,
Are you referring to one-to-one emails sent on a ticket record through the connected inbox?
Whenever a user in your portal sends an email from a record, they can choose which associated records to log this email to. In that step, you would uncheck the box for a ticket if you didn’t want the email to be documented on the ticket record:
Fictional demo data.
This can also be changed and edited after the email has been sent (see also here). It will however be a manual step.
Hope this helps!