Assuming there are four different work spaces,
how to make sure that the leads receive only a single email despite they exist in one or more work spaces.
Does this work:
Step:1. Send emails to the leads under work-space A.
Step:2. Exclude the leads of work-space A in the next run.
Step:3. Exclude the leads of A,B.
Step:4. Exclude the leads of A,B and C work-spaces.