When using Export to create a mailing list, users find that constituents are included in the exported data even though Send mail to this address is unchecked on their address record(s).
If including a query, add a filter to only include constituents with Send mail to this address checked: Address > Preferred Address > Preferred Send Mail to This Address equals Yes
If the constituents do not have any valid addresses, check the box Has no valid addresses on the Bio1/Org1 tab under This constituent. This checkbox can be used as a filter in the Export on the General tab under Include these constituents.
Use address processing in Export which considers the Send Mail to this Address checkbox: Address > Address Processing > <fields for address>