When calculating segments for a marketing effort, you might notice that some constituents get excluded even if the marketing effort universe is set to "All qualifying constituents" and there are no contact rule exclusions listed in the Exclusions tab.
There are two possible explanations for these constituents being excluded:
1) One possible reason is because the constituent cannot be contacted using the marketing effort's communication channel. For example, if the marketing effort uses the channel of mail, the constituent might not have an address or the address is marked as do not mail. 2) The constituent has a Communication preference of "Do not send" for Appeals.