Currently if you email a street and a vendor owns multiple properties on the street they get an email per house. As I don't want to harass and bombard my clients with multiple emails on the same topic it would make sense that you can email vendors on the street as an option to stop this happening
What you should be doing, is opening the list of related contacts attached to the properties, then sending them the letter/email. This way they will only show up once, and only receive one letter/email.
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