Is there a way to stop particular email address and/or email domains from syncing?

If the real estate attorney isn’t logged as a Lead or Person in Copper, then the communication wouldn’t be tracked. 

However, if you want the real estate attorney to be logged in Copper, you can still restrict access and visibility to your team through Copper’s Teams and Visibility Permissions. 

1. Set access at the individual level
   1. If you want to set visibility on individual records, you can choose one or more teams from this setting. Just keep in mind if you only set access at the individual record level, users can see all reports.
2. Set access at the team level
   1. If you'd prefer to restrict team access to multiple records or reports at once, you can do this by activating team visibility permissions. This is available to Professional and Business users. In each team's profile, you'll see a list of records and reports under 'Access & Visibility,' and you can choose what kind of access the team has to each entity type, pipeline and report. Granting Access permissions means the user can see information.