Filters in email collations do not work as expected.  For example, if you have a collation designed to send all tenants an email, but wish to break the job down to send by Manager then the filtering and selecting a manager and emailing will send emails as expected.  However If you go back and edit the job filter to remove the initial manager and select a second manager the initial manager is not removed from the collation.  Proceeding from this point would send emails to the tenants for the second manager as expected as well as the first manager who has already sent the email.